After adjusting the rack brackets, the GMA 245 Audio Panel and the GTN 650 GPS/NAV/Com slid right in. Once they are in place, a 3/32" allen wrench is inserted into a hole in the face of the units and twisted to slip the unit back into the connectors in the backplate for a secure fit. Unfortunately, the GTN 650 needs an extra long allen wrench that I don't have. Harbor freight doesn't sell them (at least in my retail store). The only extra long ones I could find were at Lowes (in the Aviation Tools department) in a set containing metric and SAE sizes. $30 later, I had the wrench I needed and a lot of other long wrenches too. It's a very nice set and will be a good addition to my workshop. The wrenches have a nice T-handle and include the long and short lengths on each wrench. Have I justified spending the $30 yet? I think so. Let's move on.
With the new wrench in hand, I tightened the GTN 650 into place. What a great fit!