A CURT custom wiring harness (also called a T connector) is a simple, plug and play electrical device that eliminates the need for cutting, splicing and soldering when installing vehicle to trailer wiring. Most vehicles do not come ready to tow. Unless your vehicle has a towing package, it is probably not equipped with a trailer wiring connector. This is where CURT's custom wiring harnesses come into play. Custom wiring harnesses plug into your vehicle's electrical system using original equipment (OEM) connectors. Our custom wiring harnesses use two or more OEM connectors to plug in at the taillight assembly and provide a standard trailer socket to allow a trailer to be plugged into your vehicle's power system.