Peepholes are small openings in a wall, door, crate, or barrel from which a person can look through. These may be on the doors of entrances to secret clubs, thieves’ dens or on the doors of gatehouses. In fictional worlds peepholes are also often found looking out from hidden rooms or from the space between walls. They may open through the eyes of a tapestry or painting. Peepholes may be used by the people who live in the walls, by door guards, and by stowaways hiding in barrels.

When designing fictional peepholes, consider if they are meant to be hidden from one side and how they are concealed. Peepholes allow light to pass through, and if they connect to a hidden room or secret chamber, any light coming from that space may reveal their existence.