We attached a CD to our upper-deck's sliding door, hoping it would keep folks from attempting to walk through the glass when the door is closed.
So far, the only time it's failed to perform to specifications was about a half an hour after we stuck it there. We were having our annual party event, and thought it advisable to make the glass more visible to those guests who might be meandering obliviously about, possessed of alcohol-impaired vision.
Alas, the occasional pair of inebriated eyes need more help than a mere CD can be expected to afford, and a guy walked SMACK into the door with a startling THUNK.
Unbelievably, minutes later, he turned around and did the exact same thing from the OTHER side of the door.
(The thing that looks like it's emerging from my cranial real estate is a stuffed toy mosquito on steroids, hanging from a roof rafter.)