http://www.smbc-comics.com/comic/work-3
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Technically, a piece of elastic is a 2-sided fitted sheet.
Bonus panel
Pro-tip: use a sharpie to mark the hem at the middle of the foot.
Extra pro-tip: To fold a fitted sheet easily and simplify putting in on the bed, first lay the sheet out. Fold it in half with the head on top of the foot and the underside as the outside. 'Nest' the fitted corners and edges from the upper half into the ones of the lower half. Fold it in half again, this time left to right (or vice versa) and nest that upper half into into the lower. You should now have the sheet folded into quarters and only a single corner, which is a lot easier to fold flat. Now you can easily fold the sheet the rest of the way, just like a flat sheet.
When putting it on the bed, place the sheet on the foot of the bed at the corner that corresponds with the corner of the sheet you nested the others into. Unfold the sheet by reversing the steps and tuck the mattress corners into the sheet.
No more dealing with a huge wad of fabric in the linen cabinet or figuring out it's orientation.