Three-way switch

three-way switch
Electrical switches installed in pairs to allow a light or appliance to be controlled from to locations.
threshold ...

Four-way Switch - Electrical switches connected between three-way switches in order to control a light from three or more stations.
Foyer - An area just inside the main exterior door for the removal of wraps, overshoes, etc.

See also: Joist, Finish, Rafters, Trimmer, House