hole 16 for fitting therein an end portion of means 15 adapted to anchor the buckle at a desired position via a cable 60 because of the provision of the h shaped hole 14 there are formed opposedly projection long projection 17 and short projection 18 the slider 4 defines a through hole 19 and is fitted on the long projection 17 the slider 4 being urged forwardly by a coil spring 20 one end of the coil spring 20 is received on the rear end face of the slider 4 mounted on the projection 17 while the other end is fitted over the short projection 18 the upper edge of the hole 16 defined a notch not shown whereas its lower edge presents a lug the notch and lug cooperate with grooves formed in an end portion of the means 15 when the means 15 is force fit in the hole 16 thereby causing the means 15 to be connected with the base 3 through the side walls 12 and 13 of the base 3 there are formd respectively in order from the front to the back and in a transversely opposed manner sectorial holes 23 and 24 for receiving edge portions 21 and 22 at front ends of the latch member 5 embossed portions 25 and 26 for preventing the tongue 2 when inserted from floating up from the floor 11 and notches 28.