elbow lever 112 see fig6 the elbow lever 112 is in turn articulated about a shaft 114 that is parallel to the sewing direction and mounted on a carrier 116 a support 118 is connected with the carrier 116 which serves to mount a pneumatic piston cylinder arrangement 120 the piston rod 122 attaches to the other arm of the elbow lever 122 while the cylinder 125 of the piston cylinder arrangement 120 is supported against the support 118 the in and out movement of the piston rod 122 adjusts the elbow lever 112 so that the guide roll 110 can be lowered onto the table top 14 or lifted from the latter in its lowered position the guide roll acts together with the drive roll 126 which is mounted beneath the table top and is connected with a drive that is not illustrated it emerges slightly through a slot 128 in the table top 14 with its peripheral surface thus the guide roll 110 and the drive roll 126 cause the entering material to be guided against the guide bar 104 with its edge the carrier 116 also holds two photoelectric transmitter and receiver arrangements 130 and 132 see fig3.