A tree stump high enough off the ground so that when you place the sheep on it (belly only) the legs dangle off the side of it, as to prevent it from running away.
Usually used for penetrating the sheep from behind, as sticking anything in a sheeps mouth is usually bad news.
John: "Yee-haw, maw! I got the sheep stump workin'! Bring out ol' betsie!"
Ol' Maw: "I told you to stop a-stickin' it to tha' sheeps, John!"