The NFL is always talking about how it cares for the safety of its players, and during the annual NFL owners meeting this week, the owners collectively agreed to increase player safety by eliminating blindside blocks, starting with the 2019 season.
Any forcible hit or contact from a blocker with his head, shoulder, or forearm is strictly prohibited under the new rules.
To clarify the rule change, the Twitter account belonging to the NFL Football Operations staff produced an educational video clarifying the new rule. It states that a blindside block “is a foul if a player initiates a block in which he is moving toward or parallel to his own end line and makes forcible contact to his opponent with his helmet, forearm, or shoulder.