What the heck is this called? And what's its purpose in life?

[GT_80]

I have the racerback for my truck. They are 100% fiberglass. I have seen some with lights mounted to them, they are OK for maybe like 5-7lbs (4 or 5 lights) but I would not go much more than that. That one in the picture will probably hold less weight because it is not attached to the roof- My racerback bolts to the roof and sides of the cab, then the top portion connects to the sides. They are all 3 pieces. Not flimsy, but not too strong either- you could reinforce the top with some stainless sheetmetal and it would probably support 15-20 lbs or more. Not a ladder rack

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