question about reinstalling map light

[popeye1978]

UPDATE:
I bought some of the fasteners and was preparing to reinstall the light when I noticed one of the posts was shorter than the others, looked like it had been snapped-off. To get a closer look I removed the support bow from the car and noticed the posts were screw-in, so used a set of Vampliers to remove them (sockets weren't properly grabbing the nut) and ...

#8 Sheet Metal Screws work just as well

 

[Rktpwrd]

From my very first reply...

They’re not rivets, they in fact thread into the roof support. Coarse thread, should accept a 7mm wrench

Regardless, glad it worked out for you.