A bartering ceremony was a ceremony performed by Tilonian merchants while bartering. It made use of a blade called a nisroh, one's skill with which determined the success of one's transactions.
In 2369, Worf was about to teach William T. Riker the Tilonian bartering ceremony as Riker prepared to go undercover as a merchant on Tilonus IV. As Worf began his demonstration, he accidentally cut Riker on the forehead, which he apologized for. (TNG: "Frame of Mind")