CURT Trailer Tongue Coupler Lock Black — 1/4-Inch Pin, 3/4-Inch Span; Padlock-Style, Includes 2 Keys

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

When a simple safety pin or standard latch won’t provide the level of protection you need, the CURT 23521 coupler lock adds a small, rugged barrier between opportunistic thieves and your trailer. Built from high-strength steel, finished in black, and supplied with two keys, this lock replaces or supplements a coupler’s retaining hardware to hold the latch closed and make unauthorized uncoupling far more difficult.

How does this lock fit my trailer’s coupler?

The CURT 23521 is engineered for latch-style couplers that accept a locking pin. It uses a 1/4-inch diameter pin and can span up to 3/4 inch across the latch opening. Measure your coupler’s gap at the latch to confirm compatibility before purchasing.

• Fits most latch-type trailer couplers that accept a pin-style lock
• Pin diameter: 1/4 inch; maximum span: 3/4 inch
• Padlock-style design seats the pin through the latch to prevent movement

What protection and durability does it offer outdoors?

This lock pairs corrosion-resistant zinc plating on the pin with a black painted finish on the body to resist the elements. The padlock-style housing also shields the pin and locking mechanism from direct exposure, helping reduce wear in marine or roadside conditions.

• High-strength steel construction for impact resistance
• Zinc-plated pin to fight rust where metal contacts metal
• Black painted body for added weather resistance and discreet appearance

How easy is it to use day-to-day?

Operation is straightforward: insert the pin through the coupler latch and turn the lock into place. The unit is designed for simple 1/4-turn activation so you can secure or remove the lock quickly when hitching or unhitching.

• Key-operated padlock design for familiar, reliable use
• 1/4-turn lock activation for fast locking and unlocking
• Includes two keys—keep a spare for emergencies or shared access

Can this lock deter theft or tampering effectively?

While no single device guarantees absolute security, the CURT 23521 substantially raises the effort required to detach your trailer when it’s coupled to a vehicle. The visible padlock-style housing serves as a deterrent, and the steel pin prevents the latch from being easily manipulated.

• Padlock-style housing limits access to the pin and locking mechanism
• Solid steel construction increases time and tools needed to breach the latch
• Visible security can discourage opportunistic theft attempts

Who is this for: The CURT 23521 is aimed at owners of small trailers, utility trailers, campers, and boats who use latch-type couplers and want a compact, reliable way to secure the coupler when hitched. It’s also a good choice for fleet operators and weekend recreation users who prefer a keyed padlock-style solution that’s simple to use and weather-resistant. Measure your coupler span and choose this model when a 1/4-inch pin and up to 3/4-inch span meet your needs.