The W3S-1939-P012 is a Wedgelock made of blue thermoplastic. The DT series wedgelock fits to fits DT series 3-way plugs and mates with the W3P-1939 wedgelock. The wedgelock ensures proper contact alignment within each connector. The secondary wedgelock is assembled at the mating interface and click into place. If by chance the secondary wedgelocks is not properly seated during assembly, it will be pressed into locked position during the mating of the connectors.