The Basic Principles of Polo
"It's not quite jumpers for goalposts..."
Polo involves two teams of 4 players. A full-size field is 300 yards long, and 160 yards wide with side boards—these are generally 6" high. There are tall collapsible goalposts at each end of the field spread 8 yards apart. The object of the game is to score the most goals by hitting the ball through the goal. Polo teams change direction after each goal in order to compensate for field and wind conditions.
A polo game has periods of play, known as chukkas (also chukkers or chuckers). Depending on the rules of the particular tournament or league, a game may have 4, 6 or 8 chukkas. Usually, each chukka is 7 minutes long with an addition 30 seconds of extra time at the end of each. Between chukkas, the players often switch to fresh ponies. In less competitive polo leagues, players may play only two ponies, alternating between them.
The game begins with each team in line forming two rows with the players in order 1, 2, 3, 4 facing the umpire in the centre of the playing field. There are two mounted umpires on the field and a referee standing on the sidelines. At the beginning of a game, one of the umpires bowls the ball in hard between the two teams. Teams change goals on ends of the field after each score or chukka. Switching sides also allows each team equal opportunity to start off with the ball on their right side, as all players must hit right-handed.
There are two basic defence techniques allowed in polo. The hook, or hooking, is when a player uses their mallet to block or interfere with an opponent's swing by hooking the mallet of the other player with their own mallet. A player may hook only if is he is on the side where the swing is being made or directly in front or behind an opponent. A foul is awarded for any hooking that does not fit this stipulation. For example, a player cannot reach over the mount of another player to hook their mallet, and this would be considered a penalty. The other defence technique is the bump, or ride-off. This is similar to a shoulder in football. It is used to break an opposing player's concentration, move him off the line of the ball, or spoil his shot. A ride-off is when one player rides his pony next to an opponent to push him away from the ball or players. This is generally only allowed when the angle of collision is not greater than 45 degrees and the ponies are riding at roughly the same speed and meet shoulder to shoulder.
Further information can be found in the Hurlingham Polo Association's 'A to Z of Polo'.