While Foxzes technique is very good and for sure should be used for the lower brick-texture parts, it takes a good chunk of time, and dosn’t always match up right with other hallway segments if you’ve used negated cylinders for the rest of the hallway instead of his technique. This is an easier and lazier technique that also works. Starting with what you already have, take a copy of the negated part and cut off the outer half.
Take it / duplicates of it and combine it with the part(s) next to the one it was taken from.
That should create a smooth edge like this.
With some textures, that should be good enough. However, in some cases, you will get overlap issues.
In cases such as these, take the original part from a segment and negate and union it to the one next to it. Only cut every-other segment to avoid gaps.
Hope that helps. If you have the time and patience for Foxzes technique, use it for sure. This is just the faster and easier way for those without.
[Edit]
Just saw someone like this older post of mine, so I figured I’d add a quick addendum. With time and more experience, there are significantly better, faster, and more practical techniques than this, though this still does work. I’d recommend anyone reading this post check out this tutorial instead: