Abstract: A fastener for a detachable mounting of flexible sheets, comprises a pair of molded members of synthetic resin which are detachably interconnectible to each other with the sheet gripped between them. One molded member is the base part and is adapted to be attached to a substrate and has an outstanding spike for passing through the sheet. The spike has a cylindrical stem, an annular flange, and a conical spike tip at its outer end. The other molded member is a slip-on member comprising a two-legged clamping fork, the legs having a least internal spacing from each other which is less than the diameter of the cylindrical stem of the other member, and a plurality of pairs of opposed recesses disposed along the confronting edges of the legs. Also, the thickness of the forked member tapers and is least at its free end.