Peephole
Small, round opening through a door
Peephole
A modern peephole, peekhole, spyhole, doorhole, magic eye, magic mirror or door viewer is a small, round opening through a door from which a viewer on the inside of a dwelling may "peek" to see directly outside the door. The lenses are made and arranged in such a way that viewing is only possible in one direction. The opening is typically no larger than the diameter of a button (0.7 inches, 18 mm). In a door, usually for apartments or hotel rooms, a peephole enables one to see outside without opening the door or revealing one's presence. Glass peepholes are often fitted with a fisheye lens to allow a wider field of view from the inside.
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