Master Lock Trailer Hitch Lock - Weather Resistant Security

In this review of the Master Lock Trailer Hitch Lock No. 377KA, the bottom line is simple: this is a practical, heavy-duty hitch lock for trailer owners who need a straightforward way to secure common coupler sizes. The lock is designed to fit 1-7/8 in, 2 in, and most 2-5/16 in trailer couplers and uses an advanced locking mechanism intended to resist picking and prying. Installation is quick and the keyed-alike option makes it convenient for users who prefer using the same key across locks, making it a sensible choice for boat trailers, utility trailers, and anyone who values rust resistance and ease of use.

Key Features

• Multi-size compatibility: Fits 1-7/8 in, 2 in, and most 2-5/16 in couplers so one lock covers the most common trailer tongues.
• Advanced locking mechanism: Designed to resist picking and prying, offering stronger theft deterrence than basic pin locks.
• Weather resistant finish: Resists rust and corrosion to hold up in outdoor and marine environments.
• Easy installation: Installs and removes quickly without tools for convenient daily use.
• Keyed alike option: Lets owners use the same key across multiple locks to reduce key clutter.

Who It's For

This hitch lock is best for owners of small to medium trailers, boat trailers, and utility trailers who need a reliable physical deterrent and want a single lock that fits several common coupler sizes. It suits users who prioritize durability and simple, tool-free installation and who appreciate a keyed-alike convenience.

Those who should look elsewhere include owners of uncommon or oversized couplers that fall outside the stated sizes, and users who need an electronic or cable-based locking system for different mounting situations. Also check fit carefully if you have a 2-5/16 in coupler, since some customers reported mixed fit results.

Pros & Cons

Pros

• Heavy-duty build provides strong deterrence and a sense of security.
• Fits multiple common coupler sizes reducing the need for several locks.
• Weather resistant finish helps prevent rust and extends service life.
• Simple, tool-free installation makes it quick to use on the road.

Cons

• Fit can be inconsistent on some 2-5/16 in couplers, so measure before purchase.
• Not a replacement for alarmed or tracking anti-theft solutions for high-risk areas.

Specifications

Our Verdict

The Master Lock 377KA is a solid, no-nonsense hitch lock for most common trailer couplers, offering strong build quality, weather resistance, and straightforward installation. It represents good value for trailer owners who want a durable mechanical lock and keyed-alike convenience, provided they confirm fit on larger 2-5/16 in couplers before buying.

Frequently Asked Questions

Will this lock fit a 2-5/16 in coupler?
It fits most 2-5/16 in couplers, but some customers reported fit issues so measure your coupler and check clearance before purchase.

Is the lock weather resistant for marine use?
Yes, the lock resists rust and corrosion and is designed for outdoor conditions, making it suitable for boat trailers.

Can I get multiple locks that use the same key?
Yes, the product is available keyed alike so you can use one key across multiple locks.