Tetrahedron (wind Direction Indicator)

A large, lightweight framework made in the shape of a tetrahedron, a triangular-shaped solid. The framework is covered with thin metal, wood, or fabric and is painted a bright color. It is mounted on a pivot so it is free to swing with the wind, and is installed near the center of an airport beside the runway, where it is easily visible from the air. The tetrahedron always points into the wind and shows pilots approaching the airport the correct direction to make their landing approach.