Abstract: A sheet securing assembly for use in releasably maintaining in extended condition over the mattress of a rectangular bed the bedsheet and mattress cover of that bed. The securing assembly comprises four straps, each mounted to one corresponding corner of the mattress. Each strap includes an elongated body. A first hook and loop fastener is positioned under the mattress to releasably anchor the strap to box mattress. A second hook and loop fastener releasably anchors the strap to the bedsheet. A third hook and loop fastener releasably anchors the strap to the mattress cover. Each strap is characterized in that they are easily released from above the bed, enabling effortless disengagement of the hook and loop fasteners without having to lift the mattress spacedly above the box mattress. The present invention is particularly effective for waterbeds.