Personal fouls (PF) include slashing, tripping, illegal body checking, cross checking, unsportsmanlike conduct, unnecessary roughness, and equipment violations. While a stick-check (where a player makes contact with the opposition player's stick in order to knock the ball loose) is legal, a slashing violation is called when a player viciously makes contact with an opposing player or his stick. An illegal body check penalty is called for any contact where the ball is further than for high school and for youth from the contact, the check is from behind, above the shoulders or below the knees, or was avoidable after the player has released the ball. Cross checking, where a player uses the shaft of his stick to push the opposition player off balance, is illegal in field lacrosse. Both unsportsmanlike conduct and unnecessary roughness are subject to the officiating crew's discretion, while equipment violations are governed strictly by regulations. Any deliberate intent to injure opponents risks immediate disqualification. The substitute must serve out the 30 seconds.