and is also mounted between the side parts 40 41 for moving the carriage 15 there is provided a double acting cylinder 18 actuatable by a pressure fluid which acts on an extension 47 which is rigidly attached to the carriage 15 which cylinder can be acted on in a known manner by compressed air or a hydraulic fluid the control of the action of the pressure fluid on the cylinder 18 for example by means of solenoid valves is well known and will not be described in detail here within the carriage 15 there is force fitted a horizontally arranged pin 19 on which a rocker 20 is swingably mounted the rocker has two arms 48 49 of equal length in each of which there is an adjustable stop 28 which limits the swinging motion of the rocker 20 on an extension 27 which extends above the front of the rocker 20 there is fastened a support angle member 21 after loosening its attachment screws the support angle member 21 can be set in different positions within a well defined region it is advisable to provide a leaf spring 51 below the support angle member 21 at its front end to which spring a pin holder 3 is fastened the pins of which thus press relatively gently against the bottom of the button 37 which is to be aligned rigidly connected to the rocker 20 is an angle member 52 visible in fig3 having lower arms 53 which form a u shape and thereby grip around the slide rod 46 four washers 54 are provided on said slide rod compression springs 16 17 are also placed on the slide rod 46.