You can customize your Lock-A-Socket rail with Easy-to-Read socket size indicators in Metric and SAE. The underside contains a full length, high-powered, no adhesive magnet, inserted into an aluminum base for mounting onto most metal surfaces. Twist-to-Lock feature securely locks your sockets onto the rail for safe storage. To lock the socket, simply turn the socket to the right. To unlock the socket, simply turn the socket to the left.