Hankie Codes originated in the Gay Community, but are sometimes used by BDSMers as well. The different colors indicate preferred activities, while the placement of the hankie(s) in the right or left pocket.
Left pocket placement signifies a Dominant and or /Top
Right pocket placement signifies a submissive and or bottom
Note: The above pocket placements are for the US only - European flaggers (those who use the hankie code) use the opposite pockets to signify:
Dominant — Top and submissive — bottom.