In what precise Rule can I read, that a linemen who leaves and returns to the TB can not block below the waist by the side (of course, considering that the blocks ocurrs when the ball has not left the TB).?
i
n the opposite direction of the original position of the ball at the snap?.
Rostrom,
You are actually asking about at least two different elements of low blocking that are sometimes legal, and sometimes illegal.
The part of 9-1-6-a that I have highlighted with bold and italicized text is the part that governs low blocking from the front or side, and toward the ball.
By not prohibiting them, sentence one allows low blocking from the side, and back toward the ball by ONLY those players in the situation described. Sentence two allows low blocks ONLY from the front by players in other situations.
9-1-6-a Exception 2 governs low blocking toward the original position of the snap. Low blocking by team any team A player AWAY from the original position of the ball, not back toward A's end line, not more than 5 yards beyond the NZ, and from the front is permitted (with a couple of exceptions, of course, but generally true).
But, the part of your question that says, "...in the opposite direction of the original position of the ball at the snap..." is confusing. Do you mean toward the ball? Or away from the ball?
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ARTICLE 6. a.
Team A prior to a change of team possession:
Linemen with initial position completely inside the tackle box may legally
block below the waist inside the tackle box until the ball leaves the tackle box.
All other Team A players are allowed to block below the waist only if the force
of the initial contact is directed from the front. “Directed from the front” is
defined as within the clock face region between “10 o’clock and 2 o’clock”
forward of the area of concentration of the player being blocked.
Exceptions:
1. Team A players may not block below the waist when the block occurs
five yards or more beyond the neutral zone.
2. Players outside the tackle box at the snap, or any time after the snap,
or in motion at the snap may not block below the waist toward the
original position of the ball at the snap.3. Once the ball has left the tackle box, a player may not block below the
waist toward his own end line.