Extra tail light socket?

When swapping over to Waggy tail lights I noticed my OEM tails had an open socket for another bulb. When I looked at the Waggy tails they had all sockets used. Is it just another mark or a directional? (The middle to the left not the little one on the right)

i was wondering the same thing when i first snagged an extra set of tail lights from the junkyards. my 95 has a spare socket on the lense not being used. i grabbed a set of waggy tail lights and the light harness a couple months ago. when i get a chance i will swap them both out. i believe the harness is the same IIRC.

EDIT: i almost forgot to mention. the extra bulb i believe is a tail, not sure if its a brake light as well.

I have both '89 and '96 Cherokees. As far as I have been able to figure the earlier Cherokees had the extra "side" tail light bulb installed when the tail light assembly was held on by bolts top and bottom. When the car body was changed over to a stud sticking out from the body for the lower mount the extra light socket no longer fit because the light assy. needed to be slid down into place instead of bolting straight in. The later light assy. has a slot at the base where the earlier ones had a hole at the bottom but can be modified to fit over the stud.

P.S. I need to stop breaking tail lights.

I didnt like that Torx at the bottom becasue when I made my new bumper is was near impossible to get at. So I just cut that bottom tab off with a hack saw and use the other 3 bolts. So do you know if it is solid when the lights are on or does it blink also? I want ot put the other bulb in and I'll just splice it to the other following light.

Is far as I can tell it's just wired into the tail light wire. It uses a smaller single filament bulb.

Okay sweet, looks like I'll just wire it up tomorrow before work. Thanks Mike.

On my 96, there are sockets and bulbs there. The wires run separately from the tail light/turn signal wires, and no controls inside the vehicle light them up.

I'm pretty sure they're hooked up to a trailer connector that's just sitting by the airbox under the hood. Although, I don't think it's factory, maybe for a similar dealer option?