A Gridiron Geometry Lesson

Laypeople may think there isn’t a big difference between spots, lines and planes, but officials need a clear understanding of those geometry terms. Very briefly, a spot is a specific point on the field. A line is a long narrow band of closely spaced spots (points) and a plane is a series of lines parallel to another and stacked to an infinite height. A line may be chalked or painted on the field, but along with spots and planes will often have to be visualized.


There are roughly 10 different types of spots defined in the rules. Almost all the spots are utilized for penalty enforcement; in fact, one of those spots carries the name “enforcement spot.” It is exactly what one would suppose it to be — the spot from which a penalty is enforced (NFHS 2-41-2; NCAA 2-25-1).

Another spot applicable to penalty enforcement is the spot of the foul (NFHS 2-41-8; NCAA 2-25-5) which requires no explanation. The end of the run (NFHS 2-41-9; NCAA 2-25-8) is also seemingly self-explanatory, but the two codes differ for legal or illegal handing. In NFHS, such handing does not result in the run ending, but in NCAA it does (NFHS 2-41-9; NCAA 2-25-8c).

Play 1:

As A1 is running beyond the neutral zone, he is grabbed by the facemask and spun around. He then hands the ball backward to A2 at team B’s 30 yardline. A2 is then tackled at team B’s 25 yardline.

Ruling 1:

In NFHS, the 15-yard penalty for the facemask foul is enforced from team B’s 25 yardline as there was only one run. In NCAA, the penalty is enforced from team B’s 30 yardline, which is where the run ended.

The previous spot (NFHS 2-41- 7; NCAA 2-25-2) is the spot from which the ball was last put in play. The succeeding spot (NFHS 2-41-10; NCAA 2-25-3) is the point at which the ball will next be put in play. All dead-ball fouls are enforced from the succeeding spot. Each time such a foul is enforced, a new succeeding spot is designated.

Understanding the basic spot (NFHS 2-41-1; NCAA 2-25-10) is essential to penalty enforcement. It is a benchmark for determining the enforcement spot on certain plays. The basic spot can be either the previous spot, the end of the run or the post scrimmage-kick spot (NFHS 2-41-6; NCAA 2-25-11).

The previous spot must be a spot between the hashmarks; if any of the other aforementioned spots occur in a side zone, they are re-located to the nearest hashmark.

The out-of-bounds spot (NFHS 2-41-5; NCAA 2-25-6) is almost always the dead-ball spot. The lone exception is under NCAA rules when a forward fumble goes out of bounds. In that case, the ball is returned to the spot of the fumble (7-2-4b-1).

Play 2:

First and 10 on team A’s 20 yardline. A1 runs to his 28 yardline, where the ball pops into the air. It hits the ground at his 33 yardline and goes out of bounds at his 35 yardline.

Ruling 2:

In NFHS, it’s team A’s ball first and 10 at the 35 yardline because that’s where the ball went out of bounds. The clock starts on the snap. In NCAA, because the fumble went forward and out of bounds, the ball is awarded to team A at the spot of A1’s fumble. That yields second and two from team A’s 28 yardline. The clock starts on the referee’s signal because the ball is returned to an inbounds spot.


There are several lines in the game and most of them are actually planes. The one that is truly a line without exception is the sideline (NFHS 2-26-6; NCAA 2-12-1). The sideline is the lateral limit of the field and extends from endline to endline. The marked line may be anywhere from 4 inches to 6 feet wide, but the “line” which delineates out of bounds is the inside edge adjacent to the field. The sideline is never a plane because the ball or the runner’s body can break the plane of the sideline as long as the runner has not touched the sideline or beyond it. The endline (NFHS 2-26-2; NCAA 2-12-3) is also a boundary line and has the same characteristics of the sideline.

The yardlines (NFHS 2-26-7; NCAA 2-12-6) are marked every five yards almost from sideline to sideline. The remaining yardlines are marked in 2-foot lengths in four places on the field (near the sidelines and hashmarks). But because they are not required on high school fields, it can make measurements a challenging proposition. Unlike the sideline, which is the inside edge of the marked line, the yardline is the nearer edge of the drawn line in the direction the offense is advancing. The chains should always be checked from one leading edge to another.


The remaining lines of note are all actually planes. That includes the line of scrimmage (NFHS 2-25; NCAA 2-21-2), which is the yardline that defines the vertical plane passing through the point of the ball nearest a team’s own goalline. The scrimmage lines are established when the ball is ready for play. The significance of the plane is primarily in determining whether or not an encroachment foul has occurred. Although the codes differ with regard to whether encroachment is a liveball foul (NCAA) or a dead-ball foul (NFHS), the foul occurs if the plane is violated.

Perhaps the best-known plane is the goalline (NFHS 2-26-3; NCAA 2-12-2). Regardless of how wide the line is drawn on the field (it may be up to 8 inches wide in NCAA), the entire line is in the end zone. It is extremely important to understand the goalline is a plane because when a ball in a runner’s possession breaks the plane of the opponent’s goalline, the ball is dead and a touchdown is scored.

Similar to the goalline, the lineto- gain (NFHS 2-26-5; NCAA 5-1-2) and the forward progress spot are technically planes, but because the ball does not become dead when those planes are penetrated, the practical application is to treat them as lines.

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