66 GMC- what is this on the roof
 

What is this on the rear center if the roof? Some kind of hole with threaded plug.

Re: 66 GMC- what is this on the roof
 

Looks like a hole with a threaded plug.

Re: 66 GMC- what is this on the roof
 

Haha, I suppose I should have asked if the hole is a factory thing and what purpose does it serve.

Re: 66 GMC- what is this on the roof
 

Usually you see something like that on the back of a boat to let the water out.. :)

Re: 66 GMC- what is this on the roof
 

Its the beer flow mount.. in Apache Junction they use to mount kegs on top and had a filler tube that went inside.

Re: 66 GMC- what is this on the roof
 

Lol. Mmmm warm beer

Re: 66 GMC- what is this on the roof
 

CB antenna hole, fixed with great stuff?

Re: 66 GMC- what is this on the roof
 

My 66 with a Service Box had a hole there for one of those rotating flashing yellow lights. My 66 was an old County Truck.

Re: 66 GMC- what is this on the roof
 

I would think a roof mounted spotlight.

Re: 66 GMC- what is this on the roof
 

I would also assume the hole was created to mount some type of roof light. If exposed to rain, it also seems water might be prevented from entering the cab depending on what the plug looks like, but it appears a great deal of water would be allowed to leak in above the inner roof panel and rust out the windshield header and A posts.