the picture is a light checker every Saturday i take this unit witch consists of blue brown red green black white red wires that connect to switches. the switches turn on different items on the trailers like side markers blinkers license plate lights and so on. i find a light out on the lynden door trailers about once ever week and a half. some times there easy fixes like corroded wirer's but other times there shorts in the line. this little devices does help the company out and it was built using all in shop parts. the blue tool box is my newest purchase i paid Matco an arm and a leg for her and i think i will name her but not sure what yet.