U-channel behind heater box

[65chevysub]

I was working on my Sub yesterday, and came across a piece of "U-Channel" behind where the heater box mounts under the cowl panel. I cleaned and repainted it, and reinstalled it, but can anyone tell me what it's for? It seems like a shield of some sort. One other thing. On Thrift-Air heater switches, there is a set of 3 terminals for the heater motor, and one single terminal below the 3. Mine has come out of the switch, as it got hot and melted the plastic terminal cover. What is this single terminal for, and has anyone used the GM heater switch/cable combo listed in the CI catalog and how does it work?
Thanks for any info