Restraint systems designed to use the mattress weight to hold the straps in place, allowing maximum versatility with all kinds of beds that may not have posts to tie straps or cuffs to. Usually sold as a kit that comes with 4 cuffs for wrists and ankles, and the adjustable straps which pass under the mattress. Breakdown of the setup is easy by detaching the cuffs and tucking the straps under the bed.