Defense block below waist

[phansen]

Originally Posted by Welpe

The rule of thumb I use for free blocking zone activity is this (assuming all other FBZ requirements are met):

*An A lineman can clip a B lineman
*An A lineman can block a B lineman below the waist
*A B lineman can block an A lineman below the waist
*An A lineman can block any B player in the back if that player is in the FBZ at the snap.

Notice that there is only one of those things that B is allowed to do.

Welpe

where does it say that B can't block in the back or clip an A lineman if all conditions of the FBZ are met?