with reference to fig1 and 2 , a skier &# 39 ; s boot 1 is retained on a ski 2 in a disengageable or releasable fashion at a front end by a front safety binding assembly or stop 4 . the boot is disengageably retained at its heel 5 by a safety rear or heel binding 6 . a lower surface 7 of the boot front end 3 rests on and is supported by a support device 8 . the support device 8 includes a stationary support 9 which is mounted to the ski and a movable support element 10 which is movably received in the stationary element 9 . the movable support element 10 protrudes from an upper surface of the stationary support to provide an upper or bearing surface 100 on which the boot rests . the bearing surface 100 projects above an upper surface 90 of the stationary support sufficiently that the front end of the boot clears the stationary support . the stationary support 9 has a width l 9 which is approximately equal but slightly less than a width l 2 of the ski 2 . with continuing reference to fig1 and 2 and further reference to fig3 - 10 , the stationary support 9 includes a base to which an upper element or cover 12 is attached . the base and upper element are made , preferably , of a tough , highly abrasion - resistant plastic material such as an acetal type resin , polypropylene , or polyamide . the base is attached , for example , to the ski by gluing , screws or other mechanical fasteners , by connection to the front binding assembly 4 , such as with a base plate 40 , or the like . the movable support element 10 is preferably made of metal , or other materials such as acetyl resin . the movable element 10 extends the entire width of the stationary support element , in the preferred embodiment . the movable element is movably received in relation to the stationary support element for movement at least transversely to the right dr ( fig3 a ) and to the left ga ( fig3 b ) relative to a longitudinal axis or plane xx ′ of symmetry of the ski . more specifically , displacement of the mobile element 10 occurs along a circular trajectory t with a radius r centered at a point o located on the plane of symmetry xx ′ under the heel of the boot . the radius r may , for example , be about 230 mm , but will typically range between 150 and 300 mm , depending on the size of the boot . the movable support element 10 has a profile which is curved with a similar radius such that it glides in a correspondingly shaped groove 13 in the stationary support 9 . in the rest position , the movable element is centered and maintained centered by a biasing device which permits sliding in the groove to the right dr and to the left ga against the biasing force of a compression spring 14 or other resilient or compressible biasing device . the groove 13 extends over the entire width of the stationary support and has a cross - section in the general shape of an inverted t . the groove includes an open central portion 130 from which a front groove 131 a and a rear groove 131 r extend forming a front projection 132 a and a rear projection 132 r which engage a top surface of the mobile support element 10 , note , in particular , fig7 . the movable support element 10 has a transverse profile whose cross - section corresponds to the cross - section of the groove 13 . the movable support element 10 extends , preferably , over the entire width of the stationary support and is also in the shape of an inverted t . the movable support element includes a transverse body 101 whose lower portion extends to the front to form a front rim 102 a and to the rear to form a rear rim 102 r ( fig1 ). the lower front and rear rims 102 a , 102 r are received in the front and rear grooves 131 a , 131 r , respectively . the spring 14 biases the movable support element 10 to a centered position . lateral displacements of the movable support element compress the spring which then urges the movable element to return to the centered position . the spring is lodged with its lower half in a lower spring housing 15 in the stationary support , more specifically in an upper surface 133 of the groove 13 . the upper surface 133 of the groove 13 is defined in the base 11 in the preferred embodiment . further , the spring 14 is lodged in an upper spring receiving housing or pocket 16 defined in a lower surface 103 of the movable support element 10 . the upper spring chambers or housing 16 has the same length as the lower spring chamber or housing 15 and is preferably slightly shorter than the length of the uncompressed spring 14 . in this manner , the spring is inserted into the upper and lower spring housings under slight compression in order to be prestressed when the movable support element is in its centered position . under lateral displacement of the movable support element 10 , the movable support element compresses the spring either to one side or to the other side of the lower spring housing in order to bias the movable element back toward its centered position . a series of stops limit side - to - side displacement of the movable support element 10 . more specifically , the base 11 defines a right stop 17 a which limits displacement of the movable support element to the right , and a left stop 17 r which limits displacement toward the left . the two base stops 17 a , 17 r cooperate with corresponding stops 18 a , 18 r defined on the movable support element 10 . in the preferred embodiment , the stops 18 a , 18 r are defined cut - outs or clearances 19 a , 19 r in the flanges 102 a , 102 r . at least one anti - friction sliding element 20 which has a low coefficient of friction is disposed between the movable support element 10 and the stationary support 9 to promote and control the lateral displacement of the movable support element relative to the stationary support . the sliding element is made of a low coefficient of friction material such as polytetrafluoroethylene ( tefe ), high - density polyethylene , polytetrafluoroethylene loaded with bronze balls , or other appropriate low friction materials . the anti - friction sliding element is constructed of a material which . has a lower coefficient of friction than does the material of which the base support 9 , particularly the portions of the base support which define the sliding groove 13 . the anti - friction element 20 is preferably made of a material having a lower coefficient of friction than the material from which the movable support element 10 is made . the anti - friction element 20 includes at least one small lower horizontal anti - friction plate 200 disposed between a lower surface 103 of the movable support element and an upper surface 133 of the lateral groove 13 . further , the anti - friction device includes a small anti - friction plate 201 a and a small rear anti - friction plate 201 r . the small front anti - friction plate 201 a is arranged between the rear surface 133 a of the front groove 131 a and the front surface 104 a of the front edge 102 a of the movable support element 10 . the small rear anti - friction plate 201 r is disposed between the front surface 133 r of the rear groove 131 r and the rear surface 104 r of the movable support element 10 . the small front anti - friction plate 201 a is disposed between the movable support element 10 and the stationary support element 9 toward the front av in such a manner that under forward force , it engages a forward edge of the movable support element to define a forward bearing or friction surface therebetween . analogously , the rear anti - friction plate 201 r is disposed between a rear edge of the movable support element and a rear edge 133 r toward the rear and serves as a bearing or stop surface between the movable and stationary support elements under a rearward force . the front anti - friction plate 201 a and the rear anti - friction plate 201 r are , preferably , extensions of the lower anti - friction plate 200 and are integrally formed therewith . the anti - friction plate assembly is fixedly mounted in the groove 13 and is bonded to the stationary support by welding , gluing , encasing , or the like . in the illustrated embodiment , the anti - friction element is retained in the groove by two lateral projections 110 a , 110 r in a central projection 110 c . of course , the front and rear anti - friction plates can be constructed as separate elements from the lower anti - friction plate 200 as illustrated in fig1 and fig1 a - 11 c . in the illustrated embodiment , the front plate 201 a and the rear plate 201 r are engaged in a corresponding transverse groove 111 a , 111 r defined in the base 11 . with reference to fig1 and 12 a , it is also contemplated that the lower anti - friction plate 200 is accompanied by only a front plate 201 a . alternately , as illustrated in fig1 and 13 a , it is also contemplated that the lower anti - friction plate 200 is accompanied by only the rear plate 201 r . with reference to fig1 , it is to be appreciated that the front anti - friction plate 201 a and the rear anti - friction plate 201 r can also be positioned between the front projection 132 a and the rear projection 132 r and the front lateral surface 101 a and the rear lateral surface 101 r ( fig1 ) of the transverse body 101 . the anti - friction element is approximately equal to the width of the sliding groove and the width of the mobile support element . thus , the anti - friction element is totally secured in the sliding groove and is protected against dirt and scratches . in the embodiments in which the front and rear anti - friction elements are located beneath the vertical holding projections 132 a , 132 r , additional protection is provided . with reference to fig1 and 15 a , the anti - friction element restrains the movable support element 10 against movement in an upward direction . a front anti - friction element 20 a , and a rear anti - friction element 20 r each have a transverse u - shaped profile . the u - shaped profile of the anti - friction elements define a bottom support surface 200 a , 200 r , a front support surface 200 a , and a rear support surface 200 r , as well as an upper front support surface 202 a , and an upper rear support surface 202 r . with reference to fig1 , the anti - friction element 20 includes a front anti - friction support element 20 a and a rear anti - friction support element 20 r . the two anti - friction support elements are independent and not joined to each other . with reference to fig1 , the base 11 is itself fabricated from the anti - friction material with the low coefficient of friction . the invention has been described with reference to the preferred embodiment . obviously , modifications and alterations will occur to others upon reading and understanding the preceding detailed description . it is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof .
a rear binding releasably clamps a heel of a boot to a ski . a front binding which engages a toe of the boot releases under lateral force towards the left or right side of the ski . a support assembly engages a sole of the ski boot to reduce frictional forces between the ski boot and ski which might impair the release of the front binding . the support device includes a stationary support which is mounted to the ski and which defines a lateral groove having a generally inverted t - shaped cross section . a movable element which is slidably received in the groove has an upper surface that supports the boot sole . a friction reducing element , such as a layer of low coefficient of friction plastic is disposed between the movable element and the stationary support such that the movable element and the toe of the boot can move laterally with minimum frictional resistance .