A system for use with a bed having a frame and a supporting surface includes a sheet having a bottom surface configured to be placed above the supporting surface and a top surface opposite the bottom surface, the sheet having a sheet engagement member positioned on the bottom surface; and a wedge comprising a wedge body having a base wall, a ramp surface, and a back wall, the ramp surface joined to the base wall to form an apex and having a ramp engagement member. The ramp engagement member is configured to engage the sheet engagement member to form a selective gliding assembly that resists movement of the sheet with respect to the ramp surface in a first direction.