The Pen Challenge

A pen has a fishing line strung through it so that it makes a loop not quite large enough to fit around the pen. You place the fishing line through the top button of a friends shirt (they do not see how you get it on), and the friend must try to get it off, it's actually quite difficult for how easy it is to get on.

Putting the pen on: Grab the chunk of the shirt around the button hole and place the fishing line loop around the chunk. Slide the pen through the hole and pull it through.

Getting the pen off: This is particularly difficult because the pen situation is difficult to see since it is attached to the top button. To get it off you must grab a chunk of your shirt and slide the loop down as far as you can, at which point you can slide the pen backwards through. I will post some diagrams for this puzzle.