Taillight bulbs, confused about how they work Options

[RoadRage]

Today I was fiddling with the car and I took one of my tail lights out and noticed there is a second brake and light bulb in the casing, and I never saw it work, I thought maybe it was meant to, so I replaced the bulb but it still was not working, So im writing to ask whats the go?

After doing some research (Looking at some pics on this forum) I saw that the OEM tail lights seem to have only 1 light working on each side, but the JDM tails have 2 brake lights.

Im hoping to get some JDM tails soon, but until then, I want to roll with 2 lights working, because it seems like a wasted light if its un-used and in my opinion two looks cooler,

I had a play and switched around where the light goes but for now im just left with the decision about which way should my lights work for now until I figure out how to get both to work



Was the inside bulb (the right tail light in the photo, that I switched) never meant to work and it was always meant to be 1 light only (left light) or do I need some wiring harness of some sort?

[The_enD]

On my car, if I have the parking/headlights on, the outer red lights up, but at a lower voltage. Just like you have your left tail on the picture above.
When I hit the brakes all four light up at full voltage. If you are behind the car it looks like the running lights brighten up, that's what I mean by lower voltage.
What you can do is splice the wire from the running light and connect it to the bulb that is not working in your case. That simple.
I was thinking of doing the same, but I shaved my third brake light and I thought it's better to have a light that only work when I hit the brakes, for safety reasons.