CURT Trailer Tongue Coupler Lock Black — Padlock-Style, 1/4-Inch Pin, Fits up to 3/4-Inch Span

The CURT 23521 black coupler lock is a padlock-style trailer tongue lock with a 1/4-inch pin and up to a 3/4-inch span that secures latch-type couplers and includes two keys.

If you tow a boat, camper, or utility trailer, a simple safety pin or non-locking latch can leave your trailer vulnerable to tampering. The CURT 23521 adds a keyed, padlock-style layer of protection by locking the coupler latch in place so the trailer remains attached only to the vehicle you choose. Built from high-strength steel with a weather-resistant finish and a zinc-plated pin, this coupler lock is designed for everyday use and visible theft deterrence.

How does this lock stop unauthorized uncoupling?

The CURT 23521 locks the coupler latch mechanism rather than only retaining a pin, preventing the latch from being released without the key. Its padlock-style housing surrounds the pin and reduces access for bolt cutters and prying tools, while the visible black finish signals added security to would-be thieves.

• Key-operated padlock design secures the latch in place.
• 1/4" diameter pin resists bending under force.
• Padlock-style body shields the pin from direct tampering.
• Included two keys allow for a spare or shared access.

Will this coupler lock fit my trailer's latch?

This model is made for latch-type couplers that accept a retaining pin up to a 3/4-inch span and a 1/4-inch diameter pin. Measure the gap of your coupler latch to confirm compatibility; if the span or hole diameter exceeds these dimensions, choose a different model.

• Fits latch-type couplers with up to 3/4" pin span.
• Pin diameter: 1/4" — standard for many trailer latches.
• Ideal for conventional ball-coupler latch retainers.
• Not for weight-distributing or unique custom coupler systems.

How durable is the lock against weather and corrosion?

CURT engineered this coupler lock to withstand outdoor exposure. The lock body carries a black painted finish to resist surface wear and the pin is zinc plated to limit corrosion where metal contacts the coupler, helping maintain reliable operation in wet or salty conditions.

• Black painted finish helps protect the housing from chips and rust.
• Zinc-plated pin reduces corrosion at the contact point.
• Heavy-duty steel construction for long-term durability.
• Simple 1/4-turn lock operation reduces internal wear.

How convenient is daily use and key management?

The CURT 23521 is designed for quick locking and unlocking during routine coupling tasks. The lock uses a straightforward 1/4-turn key action and comes with two keys so you can keep a spare in a secure place or provide a backup to a travel partner.

• 1/4-turn activation for fast operation.
• Two keys included—one spare for emergencies.
• Padlock form factor makes it easy to grasp and operate with gloves.
• Visible deterrent that doesn’t require complex procedures.

Who is this for? The CURT 23521 is aimed at owners of boats, campers, ATV trailers, and general utility trailers that use latch-type couplers with a 3/4-inch or smaller span. It fits users who want a straightforward, keyed locking solution that’s portable, durable, and simple to operate—ideal for daily drivers, weekend recreational users, and fleet vehicles seeking basic added security without complicated installation.