NCAA-Men's guidelines:

Section 2. Screening

A screen is legal action by any player with or without the ball, which, without causing contact, delays or prevents an opponent from reaching a desired position. A screener must be inbounds and maintain a normal stance with the inside of the screener's feet no wider than shoulder width apart. If a player is engaged in illegal screening tactics and there is no contact with the opponent, no foul has occurred. Players must adhere to the screening rules outlined in Rule 4-35.

A foul shall be called when:

1. A defensive player is held or pushed off of his intended path around a screen by use of the arms, legs or body.

2. A defensive player holds or pushes through the screen using the arms, legs or body.

3. The screener extends the hips or buttocks to displace the defender who is attempting to move around the screen.

4. The screener extends the legs beyond legal width and trips a defender who is attempting to move around the screen.

5. The screener sets a “blind” screen (outside the visual field) on a stationary defender that doesn’t allow the defender a normal step to move.

6. The screener sets a “blind” screen (outside the visual field) on a moving defender and doesn’t allow ample time to stop or change directions; usually one to two strides.