to one side of the traveling shoe 24 and arranged substantially parallel to the work engaging surface of the shoe a non circular aperture 44 is formed in the planar portion 42 the aperture 44 preferably taking the form a narrow straight slot elongated in the direction parallel to the traveling shoe 24 the slot may be formed with a small laterally extending branch 46 at each extremity and this is done solely to facilitate the design of a punch to produce the aperture in such a way that burrs may be eliminated at the extremities of the slot cooperating with the aperture 44 in the support bracket 40 is a projection 48 bent upwardly at a substantially right angle from the work engaging plate 34 the projection 48 is preferably formed with lateral offsets 50 at each side so that the overall thickness of the projection can match closely the width of the aperture 44 and this overall width may exceed the thickness of the sheet metal of which the work engaging plate 34 is made the projection 48 which is part of the work engaging plate 34 has a depending interlock finger 52 which extends forward of projection 48 and also is bent at an angle so that the free extremity will terminate in a downwardly bent tip 54 that is positioned over the tang 18 of the presser foot 14 the tang 18 as illustrated in fig3 and 4 is formed in its top surface 57 with a recess 56 adapted to accommodate the downwardly bent tip 54 of the interlock finger 52 to effect a.