A switch assembly consists of four rails. The two outer rails are known as the stock rails. The two inner rails are called tongue rails. One stock rail and one tongue rail form a switch. The switch assembly consisting of the above four rails is also known as "points". The tongue rails pivot about a point known as the "heel". The tongue rails of the switch assembly are firmly held by stretcher bars. The tongue rails are machined out of a standard rail section.
A sketch of the switch assembly is given in Figure.
Figure : Switch Assembly