In the gay leather community, there are many symbols to denote what you are into, and if you like to be the "Top" or the "bottom" (no, no one is the "man" or "woman"—both are men, but one "gets it" and the other "gives it."). Keys and hankies are one form of that communication.

Keys on right front mean, "I'm a bottom and I want to take a Top home."

Keys on left front mean, "I'm a Top and I want to take a bottom home."

Keys on left back mean, "I'm a Top and I want to go home with a bottom."

Keys on right back mean, "I'm a bottom and I want to go home with a Top."

Other forms of communication:

You know what kind of bondage a man likes by the kind of strap he wears on his motorcycle hat (although this has gone somewhat out of style). A leather strap connotes someone who likes leather restraints, and a chain strap is someone who likes chains. I don't know what you do about rope restraints.

You can also tell a top from a bottom by the epaulet he wears a cock ring (ring designed go around the base of the cock & balls to help maintain an erection by holding the blood in) on his motorcycle jacket. Again right=bottom, left=top.