Lights on tailgate?

My 89 K3500 has five small lamps across the tailgate near the top. When I bought it I thought someone had put them there. That was until today when I saw another truck with the same lights on the tailgate. Are they some kind of running lamp? They didn't light up when the brakes were applied. I'm asking because my truck is currently two hours away in storage, and I never drove it except to put it into storage last fall.