Blocking below the waist.

[Agreen_14]

I have a million questions since this is my first year as an NFHS official in Ohio (OHSAA). My question is about blocking below the waist, outside the free blocking zone, on defense.

A runs a sweep to the outside. B blocks the lead blocker below the waist on B's 40 yard line. A continues to advance the ball, picks up a first down, and is tackled at their own 40 yard line.

Do I give the option of enforcement from the spot of the foul or tack on 15 yards to the end of the run or something else? I could not find the answer in any of the books to this particular play, so a ruleset would also be very appriciated.

Thanks,
Austin.