Related Clues:

• Big name in caulk
• Fist bump, in slang
• High-five relative
• Handshake relative
• Nonverbal greeting
• Bump fists
• Shoe insole perhaps upside down
• Alternative greeting to a high-five
• Fist-bump
• Fist bump, colloquially
• Greeting originating among black soldiers in Vietnam
• High-five alternative
• Do a fist bump
• Rap on the knuckles?
• It's given as a greeting