A molded sliding bar buckle of the type comprising a strap retainer bar slidably mounted on an open rectangular connector frame having a grip base and a connecting bar on opposite sides of the strap retainer bar. The strap retainer bar includes a central strap engagement portion for retaining therearound one end portion of a strap and having on its back a sloped flat or substantially flat surface facing away from the grip base. The sloped surface has an upper end disposed adjacent to the connecting portion and a lower end disposed adjacent to the grip base, the upper end lying in a plane extending through a center of the thickness of the strap engagement portion. With this construction, when the strap is longitudinally tensioned with its one end portion looped around the strap engagement portion, a tensioning force is transformed substantially into a force or a vector acting in said plane in a direction to tend to move the strap retainer bar linearly toward the grip base. A component of the tensioning force which acts on the strap engagement portion to tend to rotate the strap retainer bar is substantially negligible. Thus, the strap end is held firmly against displacement.