Thanks,

It is metal,it only flexes if you push at the top bit,(both sides move out a bit).

There is nothing in it,(looks like it supposed to hold something).

That long thing is a pin and the other bit is like a stretchy watch band material and it has a hole on one side.

So a hat pin would make sense but to hold what?

The new mouse pad has all the right "rough" bits so it's behaving well now,(it's great having a 30 x 30 cm mousepad that's waterproof as I've knocked the occasional can over),