These combs are used in the Leclerc tension box to space the warp threads as they are being beamed. They are open topped so you can lay the threads directly into the comb without a threading hook. The Leclerc tension box comes with two 12 dent combs (one placed at either end of the box), but 6, 8, 10, 12, 15 dent combs can be purchased individually. Price is per comb.