This question is full of holes.

put a gap in the gap, I guess.

But how do you do that? How do you put an empty space inside an empty space?

hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmhhhhhhhmmmmmmmmmmmmmmm

I dunno

Yes

Just kidding but seriously, to breach a gap is to fix the wall and end the gap

How about the battle at Thermopylae? The Persians eventually breach the gap, aka pass, which is a gap in a naturally-occurring stone wall/rock formation. So, if someone guards a gap in a wall of somekind, and they fail to block it indefinitely, the gap in that wall will be breached.

Please remove that image. But thanks for the thought!