We witness many players setting screens with their hands centered in their chest, and elbows flaring outside the body. The principal of boxing out an opponent is simple, the inside player moves her feet to beat the player behind her to a position, in essence, screening her out from the ball. When players are improperly coached or become lazy, they tend to use their arms to hold the opponent back, rather than move the feet. If a player's arms are outside the body plane and contact occurs, she is responsible for the contact, and thus, any foul which may be charged as per Rule 6-1. Players may attain a position in which their bodies are touching each other.
Contact is also allowable to maintain position.
Remember, however, that if a player voluntarily relinquishes her spot on the floor, the opponent is not necessarily responsible. When a ball is loose on the floor, players may collide violently when attempting to secure the ball. Usually, this contact is merely incidental, no matter how severe. However, when a player secures possession of a loose ball, and an opponent subsequently makes contact, the opponent is responsible for that contact. Protect the player who has the ball.