A stair case coupler is a device used to connect two separate staircases that are located close to each other. It is typically made of metal, such as steel or aluminum, and allows the staircases to be connected securely and safely. Stair case couplers can be used to make a double staircase, a single staircase with two landings, or a spiral staircase. They can also be used to connect two separate staircases in different directions.