Using an M12 battery to test out a trailer rewire. A lot easier than having to pull the truck in just to test a couple lights. So handy! : r/MilwaukeeTool
7Pin Trailer Tester, 12V Car Towing Trailer Plug Socket Connection Tester Diagnostic Tool Trailer Towing Tow Bar Light Diagnostic Tool Battery Not Included Black for Caravan RV Recreational Vehicle Tr: Amazon.com: Tools