Is blocking someone from behind but above the waist is not a penalty?

Posted under american football blocking rules On By FCY9ZWLtmU

In gridiron football, a block in the back is an action in which a blocker contacts a non-ballcarrying member of the opposing team from behind and above the waist. The foul may be called when the area blocked is anywhere on the back. It is against the rules in most leagues, carrying a 10-yard penalty.