Fitted sheets have an elastic to wrap around the mattress and prevent it from moving too much while you sleep. While these sheets protect your mattress from body oils, spills, and other things, using a mattress protector underneath your fitted sheet is a good idea for extra protection. Flat sheets lay on top of fitted sheets to protect your duvet or comforter from body oils and tearing. Not everyone uses these, but we recommend doing so. 

The flat sheet is hemmed identically on three sides and has one larger hem on the fourth side. The wider hem folds back over your blanket, coverlet, or duvet, and can be finished with a simple stitch, hemstitch, or embroidery.