What is "pad tree"

Pad \Pad\, n. [Perh. akin to pod.]

1. A soft, or small, cushion; a mass of anything soft; stuffing.

2. A kind of cushion for writing upon, or for blotting; esp., one formed of many flat sheets of writing paper, or layers of blotting paper; a block of paper.

3. A cushion used as a saddle without a tree or frame.

4. A stuffed guard or protection; esp., one worn on the legs of horses to prevent bruising.

5. (Zo["o]l.) A cushionlike thickening of the skin one the under side of the toes of animals.

6. A floating leaf of a water lily or similar plant.

7. (Med.) A soft bag or cushion to relieve pressure, support a part, etc.

8. (Naut.) A piece of timber fixed on a beam to fit the curve of the deck.
   --W. C. Russel.

9. A measure for fish; as, sixty mackerel go to a pad; a basket of soles. [Eng.]
   --Simmonds.

10. A dwelling place, usually an apartment; one's living quarters; as, come over to my pad to watch the game.

11. A sum of money paid as a bribe to police officers, shared among them; also, the list of such officers receiving such a bribe.

    Pad cloth, a saddlecloth; a housing.

    Pad saddle. See def. 3, above.

    Pad tree (Harness Making), a piece of wood or metal which gives rigidity and shape to a harness pad.
    --Knight.

    on the pad, receiving bribes; -- of police officers.