We also have the bed slats, which are thick wooden ones that cannot move about, fixed onto strong canvas-like material webbing down both sides to comfortably fit a king single bed.
If you need them for an uncomfortable bed or one with a base that moves around on you like my other bed did.
They could go over a hard metal base that digs in or replace slats that move (like my other bed, where they weren't attached to webbing).
I'd keep them myself, but I no longer have a king single bed.
Also, I have a perfect, top-quality, acute pressure care memory foam (various pressure and sides) for a king single bed, flat or folding.
