Abstract: A strap buckle permitting slidable movement of a strap, such as a belt, therethrough in a first direction with selective locking by moving the strap in a second direction. The buckle includes a main frame with a roller mounted in the frame and covered by a pivotable cover plate. A common pin journals the roller and pivotally mounts the cover plate to the frame. The roller is rotatably journaled in the frame and is provided with a tooth-containing segment for engaging the belt against the cover plate to lock the strap in a fixed position. The roller comprises an arcuate smooth section, adjacent to toothed section, and which is rotated to lie in juxtaposition to the strap and permit slidable movement of the strap in the slot when the cover member is pivoted to an open position with respect to the frame. A pair of flats are provided on the roller to stop movement of the roller in either direction.