These are triangular fabric pockets at the corners of the fitted sheet. You insert a plastic or wooden pole into the sleeve, which then tucks under the mattress. The weight of the water holds the pole and sheet firmly in place.
These sit inside a rigid wooden frame. They require specialized California-sized sheets (Super Single, Queen, or King) that are specifically designed for the bladder's dimensions. buy waterbed sheets
Many waterbed sets have the flat sheet sewn to the fitted sheet at the foot. This "sleeping bag" style prevents the top sheet from being kicked off or lost in the frame during the night. 3. Sizing Guide for Hardside Waterbeds These are triangular fabric pockets at the corners