The straps are adjustable to fit any bed larger than a twin and it secures with a seat-belt buckle so once you get the size right the first time, it will be pre-adjusted the next time you go to put it on.
Don't forget to look after your kit, using the most appropriate cleaning materials for whatever you're working with.
Partners can be lying side-by-side, lying one on top of the other, or standing with one partner holding the other upside down.