Okay...for a southpaw this is also a very effective tactic, but reverse the punches. Imagine that line again, from chin to chin, there is an opening for the straight left (which is why that is the southpaw's primary weapon). As far as the jab-tap, you just tap it down with your lead hand, and then throw the jab over the top. Winky Wright is an expert at this. He does it all the time. And especially when fighting someone with a high guard, this is sometimes the only way to make an opening for the jab.