A returner races through a gap, but a flag comes out behind the play. To understand the call, look at where the blocker made contact, the direction of the block, and whether a second teammate was engaging the same opponent. Those details separate three fouls that are often confused.
Every ruling and example on this page uses the 2026 Official Playing Rules of the National Football League, principally Rules 12-1-3(b), 12-2-1, 12-2-5 and 14. Sources were checked on 20 September 2026. A reference such as 12-2-5 means Rule 12, Section 2, Article 5.
This is an NFL explainer. Do not transfer these exceptions or penalties to college, high school, Canadian or flag football without checking that competition's governing rulebook.
NFL 2026 Rule 12-1-3(b) prohibits blocking an opponent from behind in the back above the waist, or pushing from behind with the hands or arms in a way that affects the opponent's movement, outside the close-line exception. It also expressly covers kicking-team players while a scrimmage kick is in flight.
Example: during a punt return, a teammate catches up to a pursuing coverage player and shoves between the shoulder blades, pushing that player past the returner. That is an illegal block in the back, with a 10-yard penalty. The opponent does not have to fall over.
A grab or restriction may instead be holding. Officials identify the actual action; contact with the back is not automatically the same foul as holding.
NFL 2026 Rule 12-1-3(b) makes three specific allowances: a player's personal attempt to recover a loose ball; an opponent turning away when contact is imminent; and contact with both of the blocker's hands on the opponent's side. The rule also excepts close-line play.
Example: a blocker approaches a defender from the front, and the defender turns away just as contact is about to occur. That sequence can satisfy the turning-away exception. A blocker who approaches someone already facing away cannot create the same exception merely by saying the opponent's back was turned.
The loose-ball allowance concerns recovering the ball personally. Blocking a pursuer so that a teammate can recover is a different action. These exceptions to the back-block restriction do not excuse another foul, such as holding or prohibited low contact.
NFL 2026 Rule 12-2-1 defines clipping as blocking an opponent from behind below the waist and prohibits it against a non-runner. The penalty is 15 yards. A low block into the back of a pursuing defender's legs in the open field is the clearest example.
There are specific distinctions. Side contact, or contact after an opponent turns as the block is made, is not clipping if that opponent can see or ward off the block. When both players move in the same direction, continuous contact that begins on the side and subsequently reaches below the waist from behind is also excepted.
But an offensive blocker who rolls up onto the back or side of a defender's legs after a block commits clipping, even if the first contact was legal and even in close-line play. The entire action matters, not just its first frame.
Under NFL 2026 Rule 3-6, close-line play covers contact in the pocket area on the offensive side of the line and extends three yards into the defensive side. That area ceases to exist once the ball leaves it. It is not a general exemption for anything happening near a lineman.
Rule 12-2-1 permits offensive clipping above the knees in close-line play, but never at or below the knees. It also forbids an offensive lineman from clipping a defender above the knees when that defender was aligned opposite a different offensive lineman more than one position away and is responding to the ball moving away from the blocker.
Other blocking restrictions still apply. In particular, close-line play does not make a chop block legal. Nor should this area be confused with the separately defined tight end box used in the low-block rule.
Under NFL 2026 Rule 12-2-5, all chop blocks are illegal. The central case is an offensive double team in which one player blocks a defender at the thigh or lower while a teammate engages the defender above the waist. The low block need not come from behind, and changing which contact happens first does not make the combination legal.
Example: a guard engages a pass rusher high while a running back blocks that rusher at the thighs. That is a 15-yard chop-block foul. If the back goes low first and the guard engages high simultaneously or immediately afterward, the rule also covers that reverse sequence.
The rule excepts defender-initiated contact and incidental engagement with a blocker trying to slip or escape the defender. Officials must distinguish an offensive blocking attempt from a defender creating that contact.
NFL 2026 Rule 12-2-5 also covers a low block after a teammate's high contact has ended if that teammate is still confronting the defender. It includes a pass-protection lure: one blocker confronts the defender in a pass-blocking posture without physical engagement while another chops the defender.
The listed situations also include an offensive lineman chopping a defender after another offensive player has engaged that defender high or low. Consequently, “both players were not touching him at the same instant” is not enough to dismiss the foul.
When watching the play, follow both blockers before the low contact. A close-up of only the final collision can hide the engagement that makes the combination illegal.
A single player's low block is often called a cut block. That description does not establish whether it is legal. NFL 2026 Rule 12-2-4 restricts blocks below the waist on kick plays, after possession changes and outside the tight end box. Rules 8-4-5 and 12-2 impose additional restrictions even within that box.
A block from the side can therefore avoid the clipping definition and still be an illegal low block. Likewise, contact above the waist can avoid clipping yet qualify as a block in the back or another foul. Passing one test does not establish that the whole block was legal.
These blocking rules also distinguish opponents without the ball from the runner. A tackle from behind is not automatically clipping; the separate tackling and player-protection rules still govern that contact.
The NFL 2026 penalty summary assigns 10 yards for an illegal block in the back and 15 for clipping or a chop block. Rule 14 determines where to measure. Do not automatically subtract the penalty from either the snap or the end of the return.
Return example: a player catches a punt at his own 20 and returns to his own 40. During that return, a teammate commits the only foul, an illegal block in the back at his own 30. With no further possession change, accepted enforcement is 10 yards from the foul spot, leaving the receiving team first-and-10 at its own 20. The return foul does not by itself require another punt.
Pass example: on second-and-10 at the offense's own 40, a chop block occurs in pass protection before an incomplete pass. With no other foul, acceptance moves the ball 15 yards from the previous spot to the 25, making it second-and-25. The defense can instead decline and take third-and-10 (Rules 14-1 and 14-4-4).
Half-distance limits, end-zone fouls, fouls before a turnover and double fouls can change the outcome. See NFL penalty enforcement for those decisions.
Applying NFL 2026 Rule 12 means identifying the contact point, approach, timing and any qualifying exception. For clipping, track whether the block came from behind below the waist and whether the action continued into a roll-up. For a chop block, track the other offensive player's involvement as well.
Then separate the foul decision from the Rule 14 enforcement decision: who had possession, when the foul occurred, where it occurred and how the play ended. A spectacular gain does not settle the legality of a block elsewhere on the field, and the referee's yardage announcement alone does not explain the next ball spot.
Version note: checked on 20 September 2026 against the NFL's 2026 edition. Examples are illustrative applications, not rulings on particular games. For a different season or competition, check that edition before applying these exceptions.