Boxing out prevents opponent from getting offensive rebounds.

Boxing out is one of the best defensive tools against taller players.

Andrew Bogut(Milwaukee Bucks) playing for Australia at the World Championships

Use your arms and hands to check where the opponent is located:

Shane Battier (USA) boxing out an Italian player.

You can't raise your elbows. That's a foul!!

Sacramento Monarchs vs Detroit Shock

Marc Gasol (Spain) playing the World final vs Greece.
Marc is the brother of Memphis Grizzlies' Pau Gasol.

(*) Pictures courtesy of the National Basketball Association (NBA)