I think he's speaking metaphorically. The chapter is about the judgment of Jerusalem for her sin. The city had been physically destroyed a few years before writing this, and her walls were rubble. God is wishing there would have been enough godly people to make this judgment unnecessary. "The wall," then, by my perspective, is a metaphor of spiritual strength—those who would be willing to see the "disrepair" (spiritual breakdown), climb into the "gap" (spiritual shortcomings) and bring the nation back to God so that the covenant land and people would maintain the presence of God through their holiness. And yet no one was found who was willing to stand for truth, for the covenant, and for YHWH, and so they deserved the judgment YHWH brought upon them.

Talking about a wall, was this an actual wall? And is the gap he spoke about big? From what I’ve read, it’s a missing chunk of wall, not just a crack.