surface plane as illustrated in fig4 the jaw 9 is provided in the head thereof with a through hole 10 which is penetrated by the needle 4 as it goes to fetch the thread for the stitching in this connection the jaw 9 is given a horizontal reciprocating motion along the axis x x the motion being synchronized with the horizontal reciprocating motion of the needle 4 the needle 4 first presser foot 6 first jaw 9 constitutes an assembly that moves the material forward by an amount representing the length of the stitch this amount can obviously be varied by means of known devices contained in the body 1 in order to adjust it to the design requirements and to the material to the rear of the first presser foot 6 again supported in an overhanging fashion by the head 3 there is a second presser foot 7 movable only in a longitudinal reciprocating fashion which in its lowest position comes into contact with a fixed contact surface 8 that constitutes an integral part of the most forward portion of the working surface 5 this second presser foot has the task of keeping the previously stitched material locked and of restraining the stitch during the non sewing return movement of the needle 4 the second element which together with the needle contributes to the formation of the stitch is looping a member 11 see fig4 and 11 which comprises a hollow horizontal shaft 11 rotatably mounted on an axis shown as x x in fig4 and terminating at its.