A slidably retainable fastener assembly for securing loads to a track is provided with a retainer adapted to fit at least partly within a track slot and a member operating on the retainer, the member being positionable in at least a first position and a second position. When the member is positioned in the first position, the member causes the retainer to disengage the track slot thereby allowing the fastener to be movable within the track slot, and when the member is positioned in the second position, the member causes the retainer to engage the track slot thereby causing the fastener to remain stationary within the track slot.