Dont know either .But I have heard of holes in metal parts .Only there for handling in the assembly process.
Story was many had quit the design department .And there was a hole in the Auto part that had no
function ( To them ) Not being able to figure it out they redesigned removed the hole.
But the hole was used at the assembly line for feeding that part to the assembly .A hole for a hook.
Had to put a man punch holes in it afterwards
? Holder when inserting the strap Screw ? Getting the tension in the Strap ?