What does the box next to the driver’s step do? There is not one on the passenger side.

https://www.facebook.com/marketplace/item/415918501315473

“580 six zero three 2750 Calls are best, text is okay, messenger is not likely. I am selling/ screening for my friend. If you sound legit, I can pass your information on to him. This Willys is exceptionally good condition compared to 90 percent of the normals. Starts easy, and drives good. Minimal rust (see pics, new tires, new fuel tank, remote oil filter kit, 12 volt system. Ready to go, and has a tow bar if you don’t want to drive it home.”