CURT Trailer Tongue Coupler Lock – Black 1/4" Pin, Fits Up to 3/4" Span, Steel Padlock-Style Security

CURT 23521 is a padlock-style trailer tongue coupler lock that secures latch-type couplers with a 1/4-inch pin and up to a 3/4-inch span to deter theft while hitched.

If you tow a boat, camper, or utility trailer, a simple safety pin may not be enough to prevent tampering. The CURT 23521 couples a robust steel construction with a padlock design that locks the coupler latch into place, offering a stronger deterrent than non-locking pins. Finished in black with a zinc-plated pin, this compact lock is made to fit most latch-type trailer couplers and arrives with two keys for convenient access.

How does this lock improve trailer security when connected?

The CURT coupler lock goes beyond retaining the latch by locking it, which reduces the chance of unauthorized uncoupling. Its padlock-style housing shields the locking pin from easy tampering and the heavy-duty appearance alone discourages opportunistic theft.

• Steel construction resists cutting and bending.
• Padlock-style body covers the pin to limit pry access.
• Durable finish and plating protect moving parts.
• Two keys included to avoid lockouts.

Will this fit my trailer’s coupler and how easy is it to use?

This model is designed for latch-type couplers with a maximum span of 3/4 inch and accepts a 1/4-inch diameter pin. Operation is straightforward: slide the pin through the latch area and turn the key to lock or unlock, making it a quick addition to your hitch routine.

• Fits latch-type couplers up to 3/4" span.
• 1/4" pin diameter for standard latch holes.
• Simple 1/4-turn lock action for fast use.
• Two keys let you keep a spare for emergencies.

How does this lock hold up outdoors and over time?

The CURT 23521 is finished in black paint to resist weathering, while the pin is zinc-plated to slow corrosion where metal contacts metal. Regular inspection and basic maintenance, such as occasional lubrication of the keyway, will extend its reliable service in outdoor conditions.

• Black painted body for exterior protection.
• Zinc-plated pin reduces rust at contact points.
• Solid steel core to withstand regular use.
• Simple design minimizes parts that can fail outdoors.

What should I know about keys, replacement, and compatibility?

The lock ships with two keys so you can store a spare in a safe place or share one with a trusted person. If you lose keys, replacement or rekeying is possible through CURT or a locksmith familiar with trailer hardware; confirm model details when requesting service.

• Includes two keys for convenience and backup.
• Replacement keys or rekey service available via manufacturer or locksmith.
• Keep model number (CURT 23521) handy for compatibility checks.
• Not intended for non-latch coupler types—measure span and pin hole first.

Who is this for? The CURT 23521 coupler lock is suited for trailer owners who want a compact, easy-to-use lock that secures latch-style couplers while the trailer is hitched. It’s a practical choice for recreational boaters, RV owners, landscapers, or anyone who needs quick, visible theft deterrence and simple operation without bulky hardware.