1975 duster fuse block hold down pic needed

That's pretty much the way it works but the plastic piece on the back side of the bracket is threaded. The thumb screw is a tight fit in the threaded plastic piece, so when you turn the thumb screw 90 degrees both the screw and the plastic piece rotate together. Once turned 90 degrees, the plastic piece lines up to a slot in the bracket allowing the fuse box to swing down. Those pieces don't appear in the parts catalog. Looks like your only option is used or fabricating something.