Hi John,

We recommend using two M6 Button Head Cap Screws to install the Side Mount onto aluminum mullion.

Amazon is a good source for the M6 rivet nuts (our bracket also work with ¼-20 rivet nut). Here is a link to order them:

http://a.co/eoiNf5A

The tool is also available on Amazon:

http://a.co/iUnZqm7

The M6 rivet-nuts, installation tool, and screws can also be purchased form McMaster here:

https://www.mcmaster.com/95603A780

https://www.mcmaster.com/95603A111

https://www.mcmaster.com/#91306a671/=16c9vtg

McMaster usually have those in stock and ship the same day if you order before 5:30pm