Someone in chat mentioned that something they attempted to build a long time ago had a huge problem with 'floating' triangles. I think most builders have encountered these before - and they are, as long as you know how, so easy to deal with! A lot of builders will probably know how to deal with these, but for the sake of the people who don't, then this is for you.
I would like to point out, before I begin, that I tried multiple searches and found no threads already covering this. Thank you.

First of all, delete the segment of wall that has floating triangles above it.
Then press undo to get your wall back.

Yes, it's that simple! Below are some images for visual learners.




This is tried and tested in a game of patch level 1.33 (base game). I also used this on patch level 1.29.