Sleen Whip

Thurnus tapped on the bars of the cage with a sleen whip. "Come out, little slave," he said.

On my hands and knees I emerged from the cage, head down, crawling out onto the hot sand. It was the first time I had ever been caged. Without thinking I began to rise to my feet. The butt of the sleen whip struck me heavily, driven downward, between the shoulder blades, felling me. I lay in the hot sand, startled. I hurt. I could feel the warm sand, granular, between my fingers, on my thighs. "Master?" I asked, frightened. How had I displeased him?
Slave Girl of Gor     Book 11     Page 187

Imnak, who had returned to the tent after fastening her in place, returned to the pole. He carried a sleen whip.
Beasts of Gor     Book 12     Page 219

Karjuk stepped on the runners of his sled, and cracked his whip over the head of his snow sleen.

Ram's sled fell into line behind him.

"On!" called Imnak, taking his place behind his sled, and cracking the long-bladed sleen whip over the snow sleen, Akko's beast, which was in his traces.
Beasts of Gor     Book 12     Page 320