This is great for anyone who has a seven pole on their pickup which hasnt been used in a while and want to test it before they head down the road with a trailer. Also if you do hook up your trailer and it does not work for whatever reason, you can use this to tell if the truck is working or if its your trailer thats not working. Its a really handy tool to keep in your toolbox. Well go ahead and install it and show you how it works. Basically you install this on your seven pole as you would a trailer. Now well go through the functions and show you how it works. First well try the running lights, then the brake lights then well do the individual turn signals. This should be left turn and then right turn. Now we will try reverse. This product tests for the following functions: left and right turn, running lights, brake lights, reverse lights, and your twelve volt hot lead which is not installed on this vehicle. There you have it for part # TR20117.