Free Block Zone Question

[Niner]

There is a thing to remember about the FBZ. There are two types of blocks that are made legal in the FBZ, a block below the waist and a block in the back. However, even in the FBZ, a block below the waist must be on a defender who is on the line of scrimmage at the snap. A linebacker who at the snap is not on the line of scrimmage cannot be legal blocked below the waist even if he later charges across the LOS. He can be blocked in the back.