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					Originally Posted by JugglingReferee
					
				 
				So then in the US, the LS actually changes on a 4th-down incomplete pass? 
			
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The neutral zone stays the same, A's leading edge of the ball is B's trailing edge and vice versa.
Given only the leading edge of the ball matters for a TD, it makes sense. 
Crews I've worked on make the switch with the chains. It is called football and not inch ball, but this one is easy to get right.