the following description is merely exemplary in nature and is in no way intended to limit the invention , its application or uses . referring now to fig1 , there is shown a hood 10 which is composed of a double - layered structure wherein an outer skin 11 is piled on an inner skin 12 . both side edge portions of an upper surface of the inner skin 12 have backing plates 13 , 13 , respectively . brackets 14 , 15 are fixedly secured to each of the backing plates 13 , 13 by means of a plurality of bolts 16 , respectively . the backing plates 13 , 13 function to prevent the inner skin 12 , which has a thin thickness , from being applied with a localized load which causes the inner skin 12 to be locally deformed , thereby reinforcing the inner skin 12 around its side edge portions . the inner skin 12 , which is attached with the backing plates 13 , 13 , forms a first preferred embodiment of a vehicular body panel according to the present invention . now , a fabrication method of the inner skin 12 as the vehicular body panel is described below with reference to fig2 a to 3b . as shown in fig2 a , a pair of plate - like backing plates 13 , 13 , each of which has a plurality of apertures 17 , are prepared . next , as shown in fig2 b , a plate - shaped blank material 18 is prepared . naturally , the backing plates 13 , 13 and the blank sheet 18 may be concurrently prepared or they may be prepared at different times . it is only important that these components be prepared in time for a joining or reconciling step described below . fig3 a and 3b are views for illustrating a sequence of the reconciling step and a bending step . in fig3 a , the backing plates 13 , 13 are reconciled to the blank sheet 18 at respective predefined areas by means of an adhesive or welding , etc . in fig3 b , the blank sheet 18 and the backing plates 13 , 13 are bent along a convex bending line 21 and a concave bending line 22 , both of which pass through the respective plural aperture rows 17 , 17 , respectively , thereby obtaining the inner skin 12 shown in fig1 . a bent portion of the blank sheet 18 is solid and free from aperture . now , the structure of the operation of the backing plate forming part of the present invention is described below in detail . fig4 shows a state wherein the backing plate 13 is reconciled to the blank sheet 18 . for ease of explanation , the backing plate 13 is shown as having three apertures laterally formed in a row . the flat blank sheet 18 with the backing plate 13 , both of which are shown in fig5 a , are bent together as shown in fig5 b . this causes each aperture 17 to be deformed in a v - shaped profile . subsequently , action of the backing plate 13 with the plural apertures 17 and the blank sheet 18 is described below . in fig6 , with a given data : b 1 = the width of the blank sheet 18 , h 1 = the height and z 1 = the section modulus , the calculation is made using the formula z 1 =( b 1 )·( h 1 ) 2 / 6 . the section modulus z 1 represents the magnitude of the bending rigidity , with an increase in the magnitude of the bending rigidity causing the blank material 18 to be hardly bent . similarly , with another given data : b 2 = the width of the backing plate 13 , d = the diameter of the aperture 17 , n = the number of the apertures , h 2 = the thickness and z 2 = the section modulus , the calculation is made using the formula z 2 =( b 2 − n · d )·( h 2 ) 2 / 6 . the section modulus z 2 also represents the magnitude of the bending rigidity , with an increase in the magnitude of the bending rigidity causing the backing plate 18 to be hardly bent . when using the backing plate 13 as a reinforcing material , the backing plate 13 has an increased thickness . that is , the relationship in thickness is selected to meet h 1 & lt ; h 2 . in a case where the backing plate 13 has a larger thickness than that of the blank sheet 18 and does not have the plural apertures 17 , then the relationship is expressed by z 1 & lt ; z 2 , the presence of the backing plate 13 disturbs the bending formation of the blank sheet 18 . in the case of h 1 & lt ; h 2 , consequently , it is desired to determine the value ( n · d ), namely , the diameter of the aperture 17 and the number of apertures 17 , such that z 1 = z 2 is satisfied . this process corresponds to the step of machining the apertures in the backing plate to meet the characteristic of the blank sheet ( i . e ., so as to adjust the section modulus ( z 2 ) of the backing plate 13 relative to the section modulus ( z 1 ) of the blank sheet 18 ). now , the case of h 1 ≧ h 2 will be described . when the backing plate 13 has a lower bending rigidity than that of the blank sheet 18 , the backing plate 13 is readily bent with a resultant increased expansion or contraction following the bending operation . with a further formation of the plural apertures 17 in such a backing plate 13 , the backing plate 13 has a reduced rigidity and an increased expanding and contracting property . as a consequence , the blank sheet 18 has an improved bending fabrication property . accordingly , even when the backing plate 13 has a lower thickness than that of the blank sheet 18 , the formation of the plural apertures 17 in the backing plate 13 is useful . fig7 a to 7d are views for illustrating the sequence of variations in the shape of the aperture formed in the backing plate . fig7 a shows a cross sectional view of the blank sheet 18 and the backing plate 13 wherein the aperture 17 looks like a true circle 23 as viewed from above . fig7 b shows a cross sectional view of the blank sheet 18 and the backing plate 13 which are bent so as to protrude upward . in this instance , the aperture 17 has an elliptical profile 25 extending along an axis 24 as viewed from above . fig7 c shows a cross sectional view of the blank sheet 18 and the backing plate 13 with a profile which protrudes downward . in this instance , the aperture 17 looks like an elliptical profile 27 extending along an axis 26 as viewed from above . fig7 d shows a cross sectional view of the blank sheet 18 and the backing plate 13 which are formed by an expansion forming or a contraction forming . in this instance , the aperture 17 has a profile , which is radially expanded outward , namely , an aperture 28 which has an increase , radially expanded diameter . in this manner , with such a deformation of the aperture 17 , which is preliminarily the circle 23 , into the elongated elliptical profile 25 which is expanded in a longitudinal ( or lateral ) direction , the elongated elliptical profile 27 which is expanded in a lateral ( or longitudinal ) direction , or the aperture 28 with the increased diameter , it is to be noted that the backing plate 13 becomes intimate with the blank sheet 18 during the bending operation , namely , that the backing plate 13 is synchronized with the blank sheet 18 in the bending operation . with the backing plate 13 without such an aperture 17 , namely , with an aperture - less backing plate , the backing plate is hard to follow the bending and expanding sequences of the blank sheet 18 and is inevitably brought into an undesirable ruptured state . with the backing plate 13 formed with such an aperture 17 , these issues are successfully addressed . ( a ) to ( i ) of fig8 show examples of various backing plates . ( a ) shows a backing plate 13 having a single , large sized circle aperture 17 a . ( b ) shows a backing plate 13 having a plurality of small sized , circle apertures 17 b formed in a zigzag pattern . ( c ) shows a backing plate 13 having a plurality of small sized , rectangular apertures 17 c formed in the zigzag pattern . ( d ) shows a backing plate 13 having a plurality of oblong apertures 17 d formed in a regular pattern . ( e ) shows a backing plate 13 having a plurality of oblong apertures 17 e formed in the zigzag pattern . ( f ) shows a backing plate 13 having a plurality of elongated , rectangular apertures 17 f formed in the regular pattern . ( g ) shows a backing plate 13 having a plurality of elongated , rectangular apertures 17 g formed in the zigzag pattern . ( h ) shows a backing plate 13 having a plurality of apertures 17 h formed in a lattice pattern . ( i ) shows a backing plate 13 having a single aperture 17 i formed in an arbitrarily irregular profile . as noted above , it is thus possible to freely determine the profile of the aperture and the number of the apertures to be formed in the bending portion of the backing plate . fig9 illustrates a damper housing in a perspective view . the damper housing 30 is a cylindrically shaped vehicular component part whose upper portion is formed with a damper seat 31 . a strut damper , which forms a part of a wheel suspension unit , rests upon the damper seat 31 . the damper housing 30 is constructed of a formed product including a plurality of steel plates piled to one another . fig1 is a partial cross sectional view of the damper housing , wherein the backing plate 13 is piled to a cylindrical body 32 and the damper housing is subsequently finished by press forming the same in a single step , featuring that the backing plate 13 has a reduced thickness with the plural apertures 17 , 17 formed at bending areas , namely , at corner sections to allow the backing plate 13 to become intimate with the cylindrical body 32 having a large thickness . that is , during the press forming operation of the backing plate 13 , which has the plural apertures 17 , together with the cylindrical body 32 , the presence of the plural apertures 17 formed in the backing plate 13 with a reduced thickness allows the backing plate 13 to be adequately expanded and bent in synchronism with the formation of the cylindrical body 32 . as a result , the backing plate 13 is brought into an adequately tight contact with the cylindrical body 32 throughout an entire , overlapped area . in the illustrated embodiment described above , although the vehicular body panel has been shown and described as applied to the example of the inner skin ( stiffener ) of the hood , the present invention may have any other application unless the vehicular body panel includes a panel , which forms a part of a vehicle body , such as a door , a floor and roof , etc . in the illustrated embodiment , further , although the present invention has been shown and described as applied to the example of the vehicular component part composed of the damper housing , the present invention is not limited to the component part of that kind and may have application to component parts of the other kinds provided that each of the components parts includes a plurality of blank sheets ( steel plates ) which are piled to one another and constitute a product which is formed by the bending operation and which serves as an accessory component of a vehicle . that is , although the present invention is specifically suited for the bending operation and the product formed by bending , the present invention may also be widely used in the “ forming process ” involving forming of metal by contraction or expansion . it will thus be seen that the present invention may be applied to the vehicular body panel in a broad sense or to the vehicular component parts in a broad sense . fig1 shows a layout of a manufacturing apparatus , for the blank sheet of the vehicular body panel , according to the present invention . the manufacturing apparatus 100 for the blank sheet of the vehicular body panel is arranged to firstly rewind a strip - shaped sheet 112 from a coil 111 of metallic sheet , secondly passed through a leveler 113 for a flatness processing and finally passed through a blanking press machine , which includes main components such as upper and lower blanking die halves 140 and 120 , for punching treatment to obtain the blank sheet . in fig1 , a lower die body 121 of a lower blanking die half 120 includes a first die segment 122 , a second die segment 123 , a third die segment 124 , a fourth die segment 125 and a fifth die segment 126 . a backing plate transfer unit 130 is located between the third and forth die segments 124 and 125 and includes a thruster plate 127 and a thruster cylinder 128 . a shutter plate 131 , which forms part of the backing plate transfer unit 130 , is located between the fourth and fifth die segments 125 and 126 for swinging movement about the center of a pin 132 . the fifth die segment 126 has a through - hole 133 formed in the vicinity of the shutter plate 131 . a backing plate supporting plate 134 is located in close proximity to a distal end of the through - hole 133 and is moved upward or downward by a vertically moveable cylinder 135 . the aforementioned backing plate transfer unit 130 is thus constructed of the thruster plate 127 , the thruster cylinder 128 , the shutter plate 131 and the through - hole section 133 of the fifth die segment 126 . an upper die body 141 of an upper blanking die half 140 includes first to fifth cutter segments 142 to 146 for shearing the workpiece in mating engagement with the aforementioned first to fifth die segments 122 to 126 , respectively . stoppers 147 , which are made of rubber , are located in the vicinity of the first , second and fifth cutter segments 142 , 143 and 146 , respectively . the upper blanking die half 140 also includes a punch 148 located in a position opposing to the backing plate supporting plate 134 for caulking operation , and a gun unit 149 . the first to fifth cutter segments 142 to 146 are arranged to move downward to a position indicated by a phantom line to perform the shearing of the workpiece . the upper blanking die half 140 may be held stationary and the lower blanking die half 120 may be lifted up to shear the workpiece . now , the operation of the aforementioned upper and lower blanking die halves is described with reference to fig1 , 14 a and 14 b . in fig1 , under a condition wherein the thruster plate 127 is retracted and the shutter plate 131 is tilted downward while the upper blanking die half 140 waits in an upper position , the strip - shaped sheet 112 is fed as the workpiece through between the upper and lower blanking die halves 140 , 120 from a front side to a rear side as viewed in fig1 . in addition , a first backing plate 151 is placed on the backing plate supporting plate 134 prior to the feeding of the strip - shaped sheet 112 , subsequent to the feeding of the same or concurrently with the feeding of the same . fig1 a shows the blank sheet as viewed from above . in fig1 b , as the upper blanking die half 140 is lowered to a bottom dead center , the first cutter segment 142 is caused to slide in contact with the first die segment 122 , thereby cutting out the sheet to form a first scrap 152 . a large sized second scrap 153 is cut out from the sheet with the second and fifth cutter segments 143 , 146 , with the second scrap 153 being concurrently blanked out to form a second backing plate 154 with the third and fourth cutter segments 144 , 145 . that is , as shown in fig1 a , the sheet is blanked out to form the second scrap 153 in a condition wherein the second backing plate 154 is left . although the second backing plate 154 is identical in shape with the first backing plate 151 , the terminologies “ first ” and “ second ” are conveniently used with a view to providing an ease of differentiating these from one another . in fig1 b , further , when the upper blanking die half 140 is kept at the bottom dead center , the first backing plate 151 is brought into contact with the blank sheet 155 , thereby enabling a caulking step in a manner as will be described in detail with reference to fig1 . in fig1 a , reference numeral 156 designates caulked portions which allow the first backing plate 151 from being separated from the blank material 155 . in fig1 b , the blank material 155 , to which the first backing plate 151 is joined , is then discharged rearward with respect to the plane of the drawing when the upper blanking die half 140 is lifted upward . an area , which is indicated by a symbol e 1 , is a punched out region and an area , which is indicated by a symbol e 2 , is a mounting place . now , a joining or reconciling method for reconciling the first backing plate 151 to the blank material 155 is described with reference to fig1 a and 15b . in fig1 a , a backing plate reconciling means is constructed of a caulking mechanism 160 . the caulking mechanism 160 includes a gun 149 mounted to the upper blanking die half 140 , a punch 148 attached to the gun 149 , a vertically moveable cylinder 135 mounted to the lower blanking die half 120 , and a backing plate supporting plate 134 connected to a distal end of a piston rod 161 of the cylinder 135 . the distal end of the piston rod 161 is formed with an upwardly opening cavity segment 162 . in fig1 b , the actuation of the vertically moveable cylinder 135 causes the piston rod 161 to move upward , thereby rendering the first backing plate 151 to be brought into abutting contact with a bottom surface of the blank material 155 . then , the punch 148 is lowered with the gun 149 to protrude into the cavity segment 162 . the intrusion of a part of the first backing plate 151 into the cavity segment 162 renders the first backing plate 151 , which is held in abutting contact with the blank material 155 , to be reconciled to the blank material 155 . now , the operation of the backing plate transfer unit 130 is described with reference to fig1 . that is , when the discharging operation of the blank material has been completed and the upper blanking die half 140 remains in a waiting position , the succeeding operation is initiated . as seen in fig1 , the backing plate supporting plate 134 is lowered and the shutter plate 131 is caused to swing in a clockwise direction as shown by arrow { circle around ( 1 )} such that an edge of the shutter plate 131 fronts the through - hole 133 . then , the second backing plate 154 , which is left on the lower blanking die half 120 , is knocked up with the thruster plate 127 . in this instance , the second backing plate 154 is dropped onto the shutter plate 131 and is transferred in sliding movement as shown by arrow { circle around ( 2 )} and passes through the through - hole 133 onto the backing plate supporting plate 134 . the second backing plate 154 , which is located on the backing plate supporting plate 134 , is fed to a subsequent blank material 155 . that is , the backing plate transfer unit 130 , which is composed of the thruster plate 127 , the thruster cylinder 128 , the shutter plate 131 and the through - hole segment 133 , functions to transfer the second backing plate 154 , which remains in the blanked out area e 1 , to the mounting area e 2 . in this example , the second backing plate 154 is laterally transferred within a limited area between the upper and lower blanking die halves 140 , 120 without being discharged outside , enabling the second backing plate 154 to be reconciled to the blank sheet 155 . in the event that the scrap is removed from the upper and lower blanking die halves 140 , 120 and is cut out again at another site to form another backing plate , although it is necessary to perform several steps involving the step of cutting out the backing plate , the step of transferring the cut out backing plate , the step of keeping possession of the backing plate , and the step of avoiding loss of the backing plate , there is no need for worrying about the loss of the second backing plate 154 in the illustrated embodiment of the present invention . as shown in fig1 , during movement of the strip - shaped plate 112 at a predefined constant speed in a direction as shown by arrow { circle around ( 3 )}, first and second blank materials 155 b , 155 c are blanked out and second and third backing plates 154 , 164 are blanked out from the scrap of the first blank material 155 b and the scrap of the second blank material 155 c , respectively . subsequently , the second backing plate 154 is waited and reconciled to the second blank sheet 155 c , thereby obtaining the blank material 155 a with the backing plate joined thereto . reference numeral 156 designates caulked portions . it will now be appreciated from the foregoing description that the method of the present invention has the operating steps which are described below . in fig1 , the strip - shaped sheet 112 for the vehicular body panel is fed through the upper and lower blanking die halves 140 , 120 and , in addition thereto , the first backing plate 151 is prepared for reinforcing the vehicular body panel . this is referred to as a preparation step . in fig1 b , further , the upper blanking die half 140 is mated with the lower blanking die half 120 relative to one another for thereby obtaining the blank sheet 155 for the vehicular body panel while obtaining the second backing plate 154 , which has the same profile as the first backing plate 151 , from the second scrap 153 . this is referred to as a blanking step . in fig1 b , consecutively , the aforementioned backing plate 151 is located on the blank sheet 155 a and is reconciled thereto to provide a joined structure . this is referred to as a backing plate mounting step . in addition , the upper blanking die half 140 is removed from the lower blanking die half 120 , thereby expelling the blank sheet 155 a with the backing plate joined thereto from the die halves . this is referred to as an expelling step . it will thus be seen that it is possible to manufacture the blank sheet 155 a with the backing plate at an improved efficiency by implementing the preparation step → the blanking step → the backing plate mounting step → the discharging step → the preparation step in a repeated sequence . fig1 shows another preferred embodiment of the present invention which is modified from the unit shown in fig1 . the lower blanking die half 120 includes a palletizer 171 and a pusher 172 both of which form a backing plate feeder mechanism 170 . the backing plate 173 , which remain at the lower most position among the piled plural backing plates 173 , is sequentially pushed out as shown by arrow { circle around ( 4 )} and transferred through a through - hole 174 to be located on the backing plate supporting plate 134 . the plural backing plates 173 may be cut out either from the scrap or from a strip - shaped steel sheet . with such a backing plate feeder mechanism 170 , it is possible to manufacture the blank sheet with the backing plate at an improved efficiency by implementing the preparation step → the blanking step → the backing plate mounting step → the charging step → the preparation step in a repeated sequence . the backing plate reconciling means may involve the reconciling means such as the caulking means , the reconciling means with the adhesive , the melting means with welding or other similar reconciling means and it doesn &# 39 ; t matter about the kind of the reconciling means . obviously , various minor changes and modifications of the present invention are possible in the light of the above teaching . it is therefore to be understood that within the scope of the appended claims , the invention may be practiced otherwise than as specifically described .