When you back up your van into your garage door, that's when. Because, for whatever reason, it didn't go up all the way when you pressed the remote button.
And you checked your rearview mirror, saw nothing, so backed up at your normal speed of 80 mph.
And it damaged not only the door, but the top of your van, too. Just to distribute the wealth.
But there's more! My camera's not working, either! I was going to show you evidence of the accident in all its glory, but no go. Even after charging the battery IT ISN'T WORKING.
Oh happy day.