Abstract: A retaining device for sheet materials such as bed sheets, etc. which comprises a pair of flat panels hinged together to form an elongated member with a pair of sections foldable over each other, one of said sections having a slot formed therein to receive corner or other portions of said sheet materials to be threaded therethrough and the other of said segments having a lip portion for engagement with said threaded sheet portions whereby said threaded portion is clamped therebetween. Said device is designed to be positioned beneath a bed mattress or other cushioning means to retain said segments in clamping position with respect to said corner or threaded portion.