Pentagonal prisms have seven faces. Faces are geometric planes that form the sides, top and bottom of solid figures. The top and bottom of a pentagonal prism have identical five sided shapes called pentagons. These faces are called bases. Pentagons can be regular, meaning that all sides are identical lengths, or irregular, meaning the sides are not equal in length. The bases of the pentagonal prism are connected by five sides that are called lateral faces. In right prisms, lateral faces are rectangles.
In geometry, the term "edge" refers to the line segment that is created where two sides of a solid figure meet. To determine the number of edges, you must determine the number of faces around the shape, the number of sides around the top and the number of sides around the bottom. Pentagonal prisms have five sides on top, five on the bottom, and five lateral faces, so there are 15 edges.
Corners are called vertices (singular: vertex). Vertices are formed where three faces of the prism meet. Pentagonal prisms have five vertices on top and five on the bottom for a total of 10 vertices.
Pentagonal prisms are used in architectural designs such as the simple saltbox house. The Pentagon in Washington, D.C., is designed in the shape of a pentagon that is five stories high. Many pre-Civil War forts, such as Fort Gaines, Fort Macon and Fort Delaware, were built in the shape of a pentagon. Fire hydrants in the U.S. have pentagonal prism nuts. Glass pentagonal prisms, called penta prisms, are used in optical devices such as laser levels, telescopes, range finders, periscopes, bore sights and camera viewfinders. The pentagonal prism is also used to design interesting boxes and carrying cases for items such as pencils, trading cards and candy. (See resources.)