Portcullis: an iron grating suspended by chains and made to slide in grooves in the sides of a fortified gateway in order to
block the entrance.
A Pyramid has a polygon for a base and triangular lateral faces intersecting at a common point called the vertex. The center line from
the center of the base to the vertex is the axis. If the axis is perpendicular to the base, the pyramid is a right pyramid; otherwise it is
an oblique pyramid. A triangular pyramid has a triangular base, a square pyramid has a square base, and so on. If a portion near the
vertex has been cut off, the pyramid is truncated, or referred to as a frustum. The Pyramids of Egypt are tetrahedral, meaning they
have five sides.