I have them on the back of my vehicles, quick story here according to what my wife told me. My wife was entering the hwy when a car behind her swerved onto the side of the road and drove past kicking up rocks. It then proceeded to brake check her several times... my kids were in the car. All of a sudden this big F350, the rancher ones with a fuel tank for a tool box, pulls up next to this guy who is harassing my wife and proceeds to push him onto the shoulder. The a$$hole car driver got the point and sped off. The F350 slowed down to ensure my wife was fine and then drove off.
The F350 had a square and compass on the back window. Do not know who this old country boy was but thank you brother.