To be legally on the line and be a lineman he must be on the line, facing his opponent’s goal line, with his shoulders approximately parallel to the line of scrimmage. What defines "approximately"?
When the 'approximately' parallel rule was first put in for split ends (to be able to turn to hear signals), Mr. Adams interpreted this as up to 30 degrees. That was in writing, somewhere, but it would take me while to find it, if I could find it at all.
Until now, that only applied to eligible linemen. Now, it applies to all linemen.