Okay, does anyone know what I'm talking about? It's a sheet, made out of some material that's slippery on one side and not slippery on the other side. Then you sew one end together, so the slippery sides meet, and the not slippery sides are on the outside. This sheet is big enough to be under your bum and your belly, up towards the shoulders if you have to. And then you just put this on your bed and it helps you roll over when you're sleeping. Does anyone know what this is called, where I can get it, or just what the material is called so I can buy it and sew it myself?