You create a small opening through a wooden, plaster, or stone wall but not through metal or other harder materials. The hole is 1 inch deep plus an additional 1 inch per two caster levels above 1st (6 inches at 11th, 8 inches at 15th, to a maximum of 10 inches deep at 19th level). If the wall’s thickness is more than the depth of the hole created, the spell fails. Observing through the hole created by a peephole spell grants cover to the observer (+4 to AC, +2 to Reflex saves, and a +10 bonus on Stealth checks). Additionally, the peephole eliminates the Perception DC modifier for a wooden door and reduces the Perception DC modifier for a stone wall to +5.

The peephole spell can also be used to create a small hole in the side of a chest, a safe or lockbox, or any other container so long as the type of material and thickness are within the spell’s capabilities.