Trailer Plug Tester

I was fault finding on my trailer plug as the lights stopped working, and I didn't have anyone around to tell me if the various light were working... which was very frustrating.
So I made up this tester using LED lights and a 7 pin flat plug.

The cable is long enough so that I can sit in the driver's seat with the tester box and see if the various lights are working.

Since I made it, I have lent it to several people to use. It is very handy!

NOTE: the pin numbers on the cover are configured for Australian style 7 pin flat plug, but you could make one up for any configuration of plug, and if the pin numbering is different, you can ignore the numbers (or let me know and I can make a different cover for you... just let me know what the pin numbering is your country).