The cylinder principle is defined as the space within an imaginary cylinder occupied by a player on the court. The dimensions, and the distance between the player's feet, shall vary according to the height and size of the player.

It includes the space above the player and is limited to the boundaries of the cylinder of the defensive player or the offensive player without the ball which are:

• The front by the palms of the hands,
• The rear by the buttocks, and
• The sides by the outer edge of the arms and legs.

The hands and arms may be extended in front of the torso no further than the position of the feet and knees, with the arms bent at the elbows so that the forearms and hands are raised in the legal guarding position.

The defensive player may not enter the cylinder of the offensive player with the ball and cause an illegal contact when the offensive player is attempting a normal basketball play within the cylinder. The boundaries of the cylinder of the offensive player with the ball are:

• The front by the feet, bent knees and arms, holding the ball above the hips,
• The rear by the buttocks, and
• The sides by the outer edge of elbows and legs.

The offensive player with the ball must be allowed enough space for a normal basketball play within the cylinder. The normal basketball play includes starting a dribble, pivoting, shooting and passing.

The offensive player cannot spread the legs or arms outside of the cylinder and cause an illegal contact with the defensive player in order to gain an additional space.

Diagram 6 Cylinder Principle

During the game, each player has the right to occupy any position (cylinder) on the court not already occupied by an opponent.

This principle protects the space on the court which the player occupies and the space above when jumping vertically within that space.

When the player leaves the vertical position (cylinder) and body contact occurs with an opponent who had already established that player’s own vertical position (cylinder), the player who left the vertical position (cylinder)
is responsible for the contact.

The defensive player must not be penalised for leaving the court vertically (within the cylinder) or having the hands and arms extended above and within that player’s own cylinder.

The offensive player, whether on the court or airborne, shall not cause
contact with the defensive player in a legal guarding position by:

• Using the arms to create more space (pushing off).
• Spreading the legs or arms during or immediately after a shot for a goal.

A defensive player has established an initial legal guarding position when

• facing the opponent, and
• having both feet on the court.

The legal guarding position extends vertically above (within the cylinder) from the court to the ceiling. The defensive player may raise the arms and hands above the head or jump vertically but that player must maintain them
in a vertical position inside the imaginary cylinder.

When guarding a player who controls (holding or dribbling) the ball, the elements of time and distance do not apply.

The player with the ball must expect to be guarded and must be prepared to stop or change direction whenever an opponent takes an initial legal guarding position in front of that offensive player, even if this is done within
a fraction of a second.

The guarding (defensive) player must establish an initial legal guarding position without causing contact before establishing the defensive position.

Once the defensive player has established an initial legal guarding position, that player may move to guard the opponent, but may not extend the arms, shoulders, hips or legs to prevent the dribbler from passing by.

When judging a charge/block situation involving a player with the ball, a referee shall use the following principles: 

• The defensive player must establish an initial legal guarding position by facing the player with the ball and having both feet on the court.

• The defensive player may remain stationary, jump vertically, move laterally or backwards in order to maintain the initial legal guarding position.

• When moving to maintain the initial legal guarding position, one foot or both feet may be off the court for an instant, as long as the movement is lateral or backwards, but not towards the player with the ball.

• Contact must occur on the torso, in which case the defensive player would be considered as having been at the place of contact first.

• Having established a legal guarding position, the defensive player may turn within the cylinder to avoid injury.

In any of the above situations, the contact shall be considered as having been caused by the player with the ball

A player who does not control the ball is entitled to move freely on the court and take any position not already occupied by another player.

When guarding a player who does not control the ball, the elements of time and distance shall apply. A defensive player cannot take a position so near and/or so quickly in the path of a moving opponent that the latter does not
have sufficient time or distance either to stop or change direction.

The distance is directly proportional to the speed of the opponent, but never less than 1 normal step.

If a defensive player does not respect the elements of time and distance in taking an initial legal guarding position and contact with an opponent occurs, that player is responsible for the contact.

Once a defensive player has established an initial legal guarding position, that player may move to guard the opponent. The player may not prevent the opponent from passing by extending the arms, shoulders, hips or legs in
the opponent’s path. The player may turn within the cylinder to avoid injury.

A player who has jumped into the air from a place on the court has the right to land again at the same place.

He/she has the right to land on another place on the court provided that the landing place and the direct path between the take-off and landing place is not already occupied by an opponent(s) at the time of take-off.

If a player has taken off and landed but momentum causes contact with an opponent who has taken a legal guarding position beyond the landing place, the jumper is responsible for the contact.ponent who has taken a legal guarding position beyond the landing place, the jumper is responsible for the contact.

An opponent may not move into the path of a player after that player has jumped into the air.

Moving under a player who is in the air and causing contact is usually an unsports­manlike foul and in certain circumstances may be a disqualifying foul.

Screening is an attempt to delay or prevent an opponent without the ball from reaching a desired position on the court.

Legal screening is when the player who is screening an opponent:

• Was stationary (inside that player’s cylinder) when contact occurred.
• Had both feet on the court when contact occurred.

Illegal screening is when the player who is screening an opponent:

• Was moving when contact occurred.
• Did not give sufficient distance in setting a screen outside the field of vision of a stationary opponent when contact occurred.
• Did not respect the elements of time and distance of an opponent in motion when contact occurred.

If the screen is set within the field of vision of a stationary opponent (front or lateral), the screener may establish the screen as close as possible to the opponent, provided there is no contact.

If the screen is set outside the field of vision of a stationary opponent, the screener must permit the opponent to take 1 normal step towards the screen without making contact.

If the opponent is in motion, the elements of time and distance shall apply. The screener must leave enough space so that the player who is being screened is able to avoid the screen by stopping or changing direction.

The distance required is never less than 1 and never more than 2 normal steps.

A player who is legally screened is responsible for any contact with the player who has set the screen.

Charging is illegal personal contact, with or without the ball, by pushing or moving into an opponent’s torso.

Blocking is illegal personal contact which impedes the progress of an opponent with or without the ball.

A player who is attempting to screen is committing a blocking foul if contact occurs when moving, and the opponent is stationary or retreating.

If a player disregards the ball, faces an opponent and shifts position as the opponent shifts, that player is primarily responsible for any contact that occurs, unless other factors are involved.

The expression 'unless other factors are involved' refers to deliberate pushing, charging or holding of the player who is being screened.

It is legal for a player to extend the arm(s) or elbow(s) outside of the cylinder in taking position on the court but they must be moved inside the cylinder when an opponent attempts to pass by. If the arm(s) or elbow(s)
are outside the cylinder and contact occurs, it is blocking or holding.

The no-charge semi-circle areas are marked on the court for the purpose of designating a specific area for the interpretation of charge/block situations under the basket.

On any penetration play into the no-charge semi-circle area, any contact caused by an airborne offensive player with a defensive player inside the no-charge semi-circle shall not be called as a team control foul, unless the
offensive player is illegally using the hands, arms, legs or body. This rule applies when

• the offensive player is in control of the ball whilst airborne, and

• the offensive player attempts a shot for a goal or passes the ball, and

• the defensive player has one foot or both feet in contact with the no-charge semi-circle area.

The touching of an opponent with the hand(s) is, in itself, not necessarily a foul.

The referees shall decide whether the player who caused the contact has gained an advantage. If contact caused by a player in any way restricts the freedom of movement of an opponent, such contact is a foul.

Illegal use of the hand(s) or extended arm(s) occurs when the defensive player is in a guarding position, places the hand(s) or the arm(s) upon and remains in contact with an opponent with or without the ball, to impede the
opponent’s progress.

To repeatedly touch or 'jab' an opponent with or without the ball is a foul, as it may lead to rough play.

It is a foul by an offensive player with the ball to:

• 'Hook' or wrap an arm or an elbow around a defensive player in order to obtain an advantage.
• 'Push off' the defensive player to prevent an opponent from playing or attempting to play the ball, or to create more space.
• Use an extended forearm or hand, while dribbling, to prevent an opponent from gaining control of the ball.

It is a foul by an offensive player without the ball to 'push off' to:

• Get free to catch the ball.
• Prevent the defensive player from playing or attempting to play the ball.
• Create more space.

The principle of verticality (cylinder principle) applies also to post play.

The offensive player in the post position and the defensive player must respect each other's rights to a vertical position (cylinder).

It is a foul by an offensive or defensive player in the post position to shoulder or hip the opponent out of position or to interfere with the opponent’s freedom of movement using extended arms, shoulders, hips, legs or other parts of the body.

Illegal guarding from the rear is personal contact with an opponent, by a defensive player, from behind. The fact that the defensive player is attempting to play the ball does not justify contact with an opponent from the rear.

Holding is illegal personal contact with an opponent that interferes with an opponent’s freedom of movement. This contact (holding) can occur with any part of the body.

Pushing is illegal personal contact with any part of the body where a player forcibly moves or attempts to move an opponent with or without the ball.

Fake is any action by a player to simulate being fouled or to make theatrical exaggerated movements in order to create an opinion of being fouled and therefore gaining an advantage.