Astitchintime
I make my own fitted sheets as commercial ones are never deep enough. And I also attach some coloured tape on the ‘short side’ so I always know that it’s either top or bottom.
I’ve recently had to buy deeper fitted sheets for a king size, after acquiring a mattress topper.
Ditto for an armless sofa bed always shared by the Gdcs. We’ve always used a quilted protector for padding, plus a quilted waterproof on top, in case of accidents. And until I bought the deeper sheet, we were having the devil of a job getting the bottom sheet on. Goodness knows why I didn’t think of it before!