Sorry, typo there on my part: that should read, “(and thus, more than five ineligible receivers)”.
I guess I am confused as to the meaning of the “line of scrimmage”. I always thought it mean the 162’ wide boundary between onside and offside. Because I have seen formations that have one player in the backfield, a player wide left and two wide right, as close to that boundary as they can get onside. Add a TE and you have 9 players on the line, but three of them are a fair distance away from the nearest tackle.
The line of scrimmage is the imaginary line where the ball is placed prior to the play, extending from the ball to each sideline, and perpendicular to the sidelines, and from which it is snapped by the center to start the play.
If you look closely at the receivers who are “on the line,” you’ll see that, when they get set, not all of them are actually on the line of scrimmage; some will be set back by a yard or so. You may even notice that, as they get set, they will even signal to the official on the sideline, to confirm that they are (or are not) on the line of scrimmage.
Below is a picture from a Packers-Bears game, with the Packers’ offense set before the snap. In it, you can see that the wide receiver at the very top of the screen, and the tight end (the third man down the line from the center, standing on the hashmark, who is in more of an upright position than the crouching linemen) are both “on” the line of scrimmage; both of them are, more or less, aligned with the five “interior linemen” – the center, and the two linemen on either side of the center.
The two wide receivers in the lower part of the screen (the one standing on the “G” in the image of the down-and-distance marker, and the one standing next to the “20”) are both offset from the line of scrimmage by a yard or so, and are clearly further back than the two eligible receivers who are “on the line.”
Great example from @kenobi_65.
For a technical explanation of the line of scrimmage, and who is actually ‘on’ the line of scrimmage, from the rule book:
ARTICLE 1. SCRIMMAGE LINE
The Line of Scrimmage is the vertical plane of the yard line that passes through the forward point of the ball after it has been made ready for play.
The very next clause in the rule book:
ARTICLE 2. NEUTRAL ZONE
The Neutral Zone is the space between the forward and backward points of the ball (planes) and extends to the sidelines. It starts when the ball is ready for play
And, the following clause:
ARTICLE 3. PLAYER ON LINE OF SCRIMMAGE
A player of Team A, who is on the line of scrimmage, must have his shoulders facing Team B’s goal line.
Item 1. Non-Snapper. If he is not the snapper, no part of his body is permitted to be in the neutral zone at the snap, and his helmet must break a vertical plane that passes through the beltline of the snapper.
Item 2. Snapper. If he is the snapper, no part of his body may be beyond the Neutral Zone.
So, if a player is ‘on the line of scrimmage’, his helmet is in front of the center’s waist, but behind the back point of the ball. He may be standing, as in the example provided, or crouched, or down in a 3 or 4 point stance.
(Note that in the image provided, the left tackle of the Packers, the second guy from the top, is damn near lined up illegally, as his helmet might be behind the beltline of the center.)
Indeed; tackles, in particular, tend to line up this way – as far “offset” as they can get away with, while still being considered to be on the line – on obvious passing downs, to give them a bit of a head start on backpedaling for pass blocking. In general, the officials tend to give them a little leeway on that rule.