Real World article
(written from a Production point of view)

In a deleted or unfilmed scene from the Star Trek: Deep Space Nine episode "When It Rains...", a kro'jek was a Klingon formal adornment that could be attached as decorative piece on a Klingon Defense Force uniform. In the scene, Martok wasn't sure about wearing the kro'jek to the Star of Kahless award ceremony. (Star Trek: Deep Space Nine Companion - A Series Guide and Script Library)