Outdoor polo is played by two teams of four men mounted on specially bred polo horses and equipped with 50- to 53-inch lithe-handled polo mallets. The 3�-inch diameter willow or bamboo wood ball is hit with the side, not the head of the mallet. Object is for one team to smack the ball through 10-foot uprights set eight feet apart at either end (back line) of the 300-yard field. Each goal counts one point. The players (No. 1, No. 2, No. 3 and back) work the ball down the field, passing it back and forth and running interference for each other. Primary job of the back is to tend goal by hitting threatening shots back up the field. The No. 3 man is the playmaker and alternates between offense and defense, while No. 2 is the primary offense man, ready to take a pass and break for the opposite goal. Main job of No. 1 is to keep the enemy back out of play. No. 1 also does a great deal of the scoring. Positions are frequently interchanged in mid-play.
Basic tactical maneuver of the game is "riding off," or shouldering an enemy player away from the ball or out of play, all at top speed. Contact between the mounted players is frequent and rough so that polo horses must be trained to charge with blind obedience and endure bone-shaking collisions. Head-on charges are minimized by right-of-way rules prohibiting bumping at an angle dangerous to rider or horse.
Fouls, which occur most frequently when right of way is in contention, are punished by allowing 30- to 60-yard penalty shots at the goal. The penalized team must stay behind their back line until ball is hit, then they may ride out to stop it. The game is played in six or eight periods of 7� minutes each (chukkers). There is no time out for changing horses (each man uses four to six horses a game, changing during the three-minute rest periods between chukkers). Time out is called for broken harness, for a fallen horse or a fallen rider if he is hurt. Substitutions are allowed if rider is unable to continue game.