In American football, the offensive line can receive a variety of penalties for transgressions on the field. When the ref blows the whistle because of something an offensive lineman did, the team receives one of these penalties:
Chop blocking: This dirty play (which draws a 15-yard penalty) is when a lineman dives at an opponent’s knees anywhere outside a designated area 3 yards beyond the line of scrimmage. The same block is considered legal when it occurs within 3 yards of the line of scrimmage. (Go figure.) The worst chop block is when linemen double-team a defender; one restrains the player around the shoulders while another hits him below the waist.
Clipping: When an offensive lineman blocks an opponent from behind, hitting him in the back of the legs or in the back. The infraction costs the offense 15 yards. However, clipping is legal within 3 yards of the line of scrimmage.
Encroachment: Encroachment happens when a player enters the neutral zone before the ball is snapped and makes contact with the opposition. This is a 5-yard penalty. The offense repeats the down.
False start: A false start is when an offensive lineman who’s in a stance or set position moves prior to the snap of the ball. This is a 5-yard penalty with a replay of the down.
Helping the runner: After the ball carrier crosses the line of scrimmage, an offensive lineman can’t push or pull him forward, helping him gain extra yardage. Helping the runner is a 10-yard penalty with a replay of the down.
Holding: When an offensive lineman grabs and holds onto a defensive player, it’s called holding, and it’s one of the worst things an offensive lineman can get caught doing. Linemen are allowed to use their hands, but they can’t use them to clamp onto an opposing player and limit his movement. If a lineman is caught holding a defensive player in the NFL, the penalty is 10 yards from the line of scrimmage.
Ineligible receiver downfield: A quarterback would never throw the ball to his blockers, but the blockers can be penalized for running downfield if they aren’t trying to block defensive players. Linemen who are no longer blocking or have lost their man can’t run past the line of scrimmage when the quarterback is attempting to pass. Ineligible receiver downfield is a 5-yard penalty with a repeat of the down.
Offside: When an offensive player lines up over the designated line of scrimmage, trying to gain an edge on blocking or simply forgetting where he should be. Generally, the lineman either places his hand over the line of scrimmage or tilts his upper body over the line of scrimmage. Offside is a 5-yard penalty with a repeat of the down.