Bottom Rocker
The lower patch on the back of a motorcycle club's vest, beneath the club's insignia, declaring what territory they claim.
The Hells Angels and Mongols have spilled a lot of blood over the right to wear a "California" bottom rocker, a privilege the Angels assert is theirs alone.
Bottom Rockers
The half-full cans of warm PBR found the day (or weeks) after a party. May or may not contain cigarette butts.
"It took me a half an hour to clean up the bottom rockers this morning"