The Horseshoe itself -
It shall not weigh more than 2 pounds, 10 ounces.
It shall not exceed 7 1/4 inches in width.
It shall not exceed 7 5/8 inches in length.
On a parallel line 3/4 inch from a straightedge touching the points of the shoe, the opening of the shoe must not exceed 3 1/2 inches.
The Rules -
Each player pitches both shoes followed by the opponent's two shoes.
In pitching a shoe, the player may not cross the foul line.
When playing teams, half the team throws from one stake and half throws from the other.
Games can be played to 40 points in a point limit game or 40 shoes in a shoe limit game. In the shoe limit game the player with the highest points wins. If a tie exists then each player can take a half win or a two inning tie breaker can be thrown.
Scoring -
Any shoe must be within one horseshoe-width (measured across the outside of the open end of the shoe) of the stake to be considered for points. (Official rules call for 6 inches max).
The closest shoe to the stake gets 1 point.
If you have two shoes closer than any of your opponent's, you get 2 points.
Ringers are worth 3 points each and must completely encircle the stake so the ends can be touched with a straight-edge without touching the stake.
If you have the closest shoe and a ringer, it's 4 points.
If your opponent throws a ringer on top of yours, they cancel and no points are scored.
Leaners are worth 1 point and are considered closer than any adjacent shoe except ringers.