When a character is nude but partially covered by a sheet. The sheet doesn't need to cover any erogenous zones to qualify for this tag. If a character is covered to the point where it's impossible to tell if she is wearing underwear under the sheet then use your best discretion.
Though thicker, this tag also currently covers blankets. This tag shares some overlap with under covers.
The following tags are aliased to this tag: nude_sheet (learn more).
This tag implicates bed_sheet (learn more).