Coupler Lock

Discourage would-be trailer thieves and their prying, picking, and tow-away theft attempts.  

Master Lock’s Die-cast coupler lock M378DAT locks solidly onto 1-7/8 inch, 2 inch, and 2-5/16 inch couplers from a wide variety of brands, including Atwood, Reese, Fulton, Dutton-Lainson, Putnam, Marvel, Acme and Ideal.   

Made of corrosion and rust-resistant materials for long-term durability, it’s easy to install and remove. Most importantly, it features an advanced locking mechanism that leaves quick-grab thieves with little option but to move on and leave your trailer alone. 

Features 

• Three-position Locking Mechanism  

• Secure fit and easy installation  

• Anodized aluminum construction    

• Corrosion and rust-resistant silver powder coat finish  

• Hardened steel shackle housing spring-loaded locking device 

• Works with couplers that have flat lips less than 5/8 inch wide.  

• Comes with two keys  

• Key-alike capability 

Easy to Install, Lock, and Remove 

The M378DAT lock features a ball that slides under your trailer coupler and a Shackle (hardened steel pin) that can either slide freely or act as a ratcheting device to hold itself firmly in place against your coupler.  

The Three-position locking mechanism features three dots around your keyhole, a quarter-turn apart, which represent a specific position: 

• Position 1: The pin can slide freely back and forth  

• Position 2: The pin ratchets forward and won’t slide backward.  

• Position 3: Deadlock. Your ratchet is locked firmly in place, leaving little or no room for thieves to use their tools.  

• Return to Position 1 to unlock and remove the coupler lock.