Training harnesses were used by the thralls of Triskelion in sessions of combat training. They consisted of straps wrapped around the thrall's shoulders and waist. There were two color schemes in the design: black, worn by males, and silver (with laces) worn by the females.

James T. Kirk, Pavel Chekov, Lars, and Kloog wore black training harnesses, whereas the male Andorian thrall did not wear a harness. Silver harnesses were worn by Uhura, Shahna, and Tamoon.

Chekov used his training harness to tie up Tamoon during the landing party's nearly successful attempt to escape their quarters. (TOS: "The Gamesters of Triskelion")