You searched for: “periscope
periscope (s) (noun), periscopes (pl)
1. An optical instrument that provides a view of an otherwise obstructed field.
2. A long tubular optical instrument; for example, on a submarine, that uses lenses, prisms, and mirrors to allow a viewer to see objects not in a direct line of sight.
3. An optical instrument for viewing objects that are above the level of direct sight or in an otherwise obstructed field of vision, consisting essentially of a tube with an arrangement of prisms or mirrors and, usually, lenses; used especially in submarines.
A man uses a periscope to see construction that is going on the other side of a wooden wall.
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A man is looking over a fence at the construction of an apartment building that is beginning in his neighborhood.