Examples from the rule book:
Approved Ruling 8-2-1
I. Ball carrier A1, while attempting to score, strikes the pylon located on the
right intersection of the goal line and sideline with his foot. He is carrying
the ball in his right arm, which is extended over the sideline. RULING:
Whether or not a touchdown is scored depends on the forward progress
of the ball as related to the goal line when the ball becomes dead by rule
(Rules 4-2-4-d and 5-1-3-a).
II. Ball carrier A1, advancing in the field of play, becomes airborne at the two-
yard line. His first contact with the ground is out of bounds three yards
beyond the goal line. The ball, in possession of the ball carrier, passes over
the pylon. RULING: Touchdown (Rule 4-2-4-d).
III. The ball, in possession of airborne ball carrier A21, crosses the sideline
above the one-yard line, continues beyond the pylon and is then declared
dead out of bounds in possession of A21. RULING: Ball is declared out of
bounds at the one-yard line (Rules 2-12-1 and 4-2-4-d).
IV. Quarterback A12 completes a forward pass to a teammate who is standing
in Team B's end zone. (a) A12 is beyond the neutral zone when he releases
the ball. (b) The receiver is wearing uniform number 73. RULING: In (a)
and (b) the result of the play is a touchdown. The penalty is completed
according to Team B's options.
V. Ball carrier A22 dives for the goal line at the B-1. The ball in his possession
(a) touches the pylon; (b) goes over the top of the pylon; (c) crosses the goal
line inside the pylon. A22 then first contacts the ground out of bounds
three yards beyond the goal line. RULING: (a), (b) and (c) Touchdown in
all three. The ball in A22's possession has broken the plane of the goal line
in all three scenarios.
VI. Ball carrier A22 heads for the right-hand pylon at the goal line. At the
B-2 he dives or is blocked into the air by an opponent. The ball in A22's
right hand crosses the sideline at the B-1 and passes outside the pylon, and
then A22 (a) touches the pylon with his foot or left hand; (b) first touches
the ground out of bounds three yards beyond the goal line. RULING: (a)
Touchdown. The goal-line plane is extended since A22 touches the pylon.
(b) Not a touchdown. The goal-line plane is not extended because A22 did
not touch either the pylon or the ground in the end zone. The ball is ruled
out of bounds at the B-1.
VII. Ball carrier A22 heads for the right-hand pylon at the goal line. The ball
in his right hand crosses the extension of the goal line outside (i.e., to the
right of) the pylon, and then A22 steps (a) on the goal line; (b) on the
sideline inches short of the goal line. RULING: (a) Touchdown. The goal-
line plane is extended because A22 touches the ground in the end zone. (b)
Not a touchdown. The goal-line plane is not extended. The ball is ruled
out of bounds at the crossing point.
VIII. Ball carrier A22 heads for the right-hand pylon at the goal line. The ball
is in his right hand. His foot hits the pylon just before the ball crosses (a)
the pylon or (b) the extension of the goal line just to the right (outside) of
the pylon. RULING: (a) and (b) No touchdown in either case. Because
the pylon is out of bounds the ball is dead when A22's foot hits it. Thus in
both cases the ball is dead before it crosses the goal line.
IX. Ball carrier A1 is hit and his forward progress stopped inbounds near the
goal line at the sideline to his right. When he is stopped he has the ball
in his right hand extended beyond the goal line (a) inside the pylon; (b)
outside the pylon. RULING: (a) Touchdown. The ball became dead when
he extended it beyond the goal-line plane. (b) Not a touchdown, because
no part of his body touches either the pylon or the end zone. In this case
the goal-line plane is not extended.