no. 747 double stretcher hook gundlach no. 747 double stretcher hook this innovative, lightweight tool stretches from the floor, not from the wall, thereby eliminating tubes, the tail block assembly and the heavy, cumbersome carrying case. double prong design ensures the best grip in oriented strand board (osb) and similar subfloors. caution: use only on wood subfloors. note: use no. 747 double stretcher hook with any stretcher head. (an adapter tube is necessary with taylor stretchers.)