referring now to the figures of the drawings in detail and first , particularly , to fig1 and 2 thereof , there is seen a front lay 10 and a top lay 11 of a feeder of a sheet - fed printing press . the front lay 10 and the top lay 11 are combined by a screwed joint 12 into a structural unit which is pivotable via a supporting part 14 by a front lay shaft 13 . as is shown in fig2 and 3 , the supporting part 14 is screwed to the front lay shaft 13 by two bolts 34 and 35 , so that rotation of the front lay shaft 13 about the longitudinal axis 36 thereof simultaneously effects a corresponding pivoting movement of the supporting part 14 , with the front and top lays 10 and 11 fixed thereto . the front lay shaft 13 is actuated by a motor in a conventional manner which is therefore not otherwise specifically shown . the front lay shaft 13 is mounted with rolling contact at least at two points in a printing press housing 39 . a roller bearing in this regard is shown in fig1 and is identified by reference numeral 40 . as is apparent , in particular , from fig2 and 3 , a vertically oriented push rod 18 acts with an upper end thereof on the screwed joint 12 . the push rod 18 serves for vertically adjusting the combination of the front lay 10 and the top lay 11 with respect to the supporting part 14 and the front lay shaft 13 connected to the latter . a vertical distance a between a surface 19 of the supporting part 14 and the top lay 11 is represented fig2 and 3 . the distance a is varied depending upon the grammage of the non - illustrated sheets to be processed . for example , for lightweight grammages , a correspondingly small vertical spacing akin of the top lay 11 in fig2 is to be selected . by contrast , in the case of heavier grammages , a higher position of the front lay 11 is to be preferred as is seen in fig3 which results in a correspondingly greater vertical spacing a max . as is illustrated in particular by fig1 a horizontally oriented rod drive 20 is disposed so that it is movable in longitudinal direction in the interior of the front lay shaft 13 and concentrically therewith . a free front end of the rod drive 20 is connected by bolts 21 and 22 to a wedge - like slide 23 . the wedge - like slide 23 has an operating surface 24 which extends obliquely and by virtue of which it is provided with the wedge shape thereof . the wedge - like slide 23 and the operating surface 24 thereof are respectively operatively connected to a sliding piece 25 which is fixed to the lower end of the push rod 18 . for this purpose , the lower end 26 of the push - rod engages in a recess 27 formed in the sliding piece 25 and is thereby anchored to the latter , as is seen in fig2 and 3 . due to a displacement of the rod drive 20 and , therefore , of the wedge - like slide 23 in the direction of an arrow 28 , the push rod 18 and , therefore , also the top lay 11 , including the front lay 10 connected to the latter ( as seen in fig2 ) is adjusted in the direction of an arrow 29 , i . e ., vertically upwardly , via the oblique surface 24 of the wedge - like slide 23 cooperating with the sliding piece 25 . if the rod drive 20 and the wedge - like slide 23 are moved in the direction of an arrow 30 ( seen in fig1 ), the push rod 18 and the combination of the front lay 10 and the top lay 11 are reset ( in a direction of an arrow 31 ) into the initial position that can be seen from fig2 . the restoring force required for this purpose is applied by a prestressed compression spring 32 ( see fig2 and 3 ) which is supported at the top thereof on the supporting part 14 , and at the bottom thereof on a disk 33 firmly connected to the push rod 18 . in order to operate the rod drive 20 , a spindle drive disposed coaxially with the front lay shaft 13 is provided , and includes a spindle 37 and a spindle nut 38 enclosing the latter concentrically . the spindle nut 38 is mounted on the front lay shaft 13 by two radial ball bearings 41 and 42 and an axial ball bearing 43 and secured against rotation by a torque support 44 . a threaded connection 45 is provided between the spindle 37 and the spindle nut 38 . at the free end of the spindle 37 ( on the side of the rod drive 20 ), the spindle 37 is mounted on the rod drive 20 by a ball bearing 46 . at the same time , the ball bearing 46 produces a formlocking connection in the axial direction 28 , 30 between the spindle 37 and the rod drive 20 . in this regard , it is noted that a form - locking connection is one which connects two elements together due to the shape of the elements themselves , as opposed to a forcelocking connection , which locks the elements together by force external to the elements . the spindle 37 can be set into rotation by an electric motor 15 via a gear mechanism or transmission 16 , 17 . because of the threaded connection 45 to the spindle nut 38 , in this case , the spindle 37 is simultaneously moved in the direction of arrow 28 and 30 , respectively , and consequently actuates the rod drive 20 accordingly via the axial bearing 46 . due to the connection 21 , 22 between the rod drive 20 and the wedge - like slide 23 , the wedge slide 23 is thereby accordingly actuated and , as explained above hereinbefore , adjusts the height of the front and the top lays 10 and 11 via the sliding piece 25 and the push rod 18 .