Suppose you're at a concert at the National Arts Centre and suddenly one of the lenses pops out of your glasses because the little screw that holds the frame shut has fallen out. And suppose you can't find the stupid screw, and even if you could you don't have a teeny little screwdriver, nor do you a piece of fine wire and a pair of pliers.
But suppose you have a binder clip!
If that's the case, no problem. On with the show.