AC Vent Door Eye Loop

[tucsonjwt]

I am putting back together the interior of my 83 C20 with factory ac and I can't remember what this center loop feature is for. I think the silver colored u shaped hook with the teflon speed nuts attaches to the vacuum canister bracket, but I don't know if this center loop connects to anything. Can anyone identify the purpose and connection (if any) on the circled loop on the vent door? Thanks.