I have thought about this idea of attaching a sign to somebody's truck. It would be one of those douche bag types who has half or more of their identity tied to their truck. The way this sign would work is that a spring would pull it up when it's parked, resulting in not being able to see it when parked and standing on any side of the truck. However, when the truck is driving, the sign would catch the draft and be pushed back into a visible position. I would put a message like this:

BIG TRUCK

SMALL PENIS

The people driving behind him would be laughing. I guess eventually someone would let him know. Unfortunately, such designs generally take testing and tinkering to get working right. You'd have to be lucky to get it right the first time.

Done this. Super glued a shitty plastic dollar store whistle to a lower control arm of this cunt that thought it was fun to play practical jokes on everyone even if he didn't know you.

Took him a while to figure it out. This was second place to: Cunt Neighbors, they go out for the night of drinking which they will come home at 2am and blast the stereo and pass out. I opened their back door which was their kitchen, showing the local racoons and then throwing cat food into the kitchen. quietly closing the door.

No loud music that night.

If you drive over the potholes in a nigger neighborhood just right, the fucking thing will play Camptown Races. ..doo dah, doo dah.

Reminds me of attaching heavy duty zip ties to the drive shaft of RWD vehicles.