Anyone know what this is under the dash?

In 1975 and 1976 Chrysler changed the fixed bracket to a hinged bracket. A slot in the fuse box slides down through the tab on the bracket. A thumb screw is turned 90 degrees to allow the fuse box to swing down. This made for better access to the fuse box than earlier models. After 50 years the plastic threaded fastener found on the back side of the bracket is often broken, cracked or missing.