In a pinch, you can use queen-sized sheets on a full bed. The top sheet can be tucked in a bit more than usual to manage the excess material. Use elastic sheet straps on the bottom sheet -- the fitted sheet -- to take up excess slack.
While actual sheet measurements vary from brand to brand, queen sheets are always a bit larger than full-size sheets since a queen mattress is larger. A queen top sheet, for instance, averages 90 inches wide and 102 inches long, while the same brand in a full size may be 81 inches wide, 96 inches long. The excess really makes a difference on the fitted sheet -- a queen sheet brand that measures 60 inches wide and 80 inches long is only 54 inches wide, 75 inches long in the version made for a full-size bed.
Dealing With the Excess
The top sheet requires no special treatment when using a queen sheet on a full bed; simply tuck in the excess material. When making the bed, line the top of the sheet up as far as you'd like it to go toward the head of the bed, almost reaching the top. Tuck in the excess material on the sides and foot of the bed.
Fidgeting With the Fitted Sheet
Since the fitted sheet is designed to fit the mattress perfectly, the fit will be a bit sloppy when using a queen sheet on a full bed. To prevent the sheet from bunching up or pulling off at the corners, use elastic sheet straps to hold the sheet in place. These straps cross the bed in an X shape, under the mattress. Clips at each end of the elastic straps grip the sheet under the mattress, making them fit more snugly.
If you don't mind a minor amount of sewing, stitch short elastic straps 5 or 6 inches from each corner of the mattress, so they fit diagonally on each corner along the bottom or open end of the sheets. The straps hold the fitted sheet onto the bottom of the full mattress.