...so ya can tell which gun ya have by feel in the dark. If ya grab a twelve gauge and some 20 gauge shells the shells will feed past the receiver and go down the barrel hanging up where the barrel narrows. If ya aren't aware of the hangup, the next time you fire the shotgun it will explode in your hands.
Liberals are like a "Slinky". Totally useless, but somehow ya can't help but smile when you see one tumble down a flight of stairs!