Protect Your Trailer When it’s Not in Tow. Protect your trailer from theft with trailer coupler locks. These locks come in handy when you want to drive your tow vehicle separate from your trailer. At a jobsite and want to leave your trailer behind while you go to lunch or head out for a missing part? Or you’ve hauled your trailer to your campsite, but need to run out for supplies. Coupler locks allow you to secure your trailer while you’re away. REESE® Towpower makes a variety of trailer and coupler locks for a verity of fits and applications.