Hardside Waterbed Padded Rails (sides only) Waterbed Padded Side Rails. One size fits all Polyvinyl channel - Unbreakable rail for years of dependability regardless of the thickness of the bed frame. 2-way padded rails cover the (longer) side rails of your hardsided waterbed and protect you as you get into and out of bed. Made in standard padding thickness and covered with durable vinyl, these rails will last for years. Standard length rails will fit any hardside waterbed: Waterbed King (California King), Waterbed Queen, or Super Single hardside waterbeds.