Something I made while bored a while ago. I figure someone might use it.
If you have trouble moving them onto the grid, select everything, select the vertex edit tool, select everything and drag a corner vertex to where you want it.
Texturing these is a bit of a pain, but what I do is select one side (of one section), rotate the UVs until they align with the edges, click 'Fit', then change the Y scale to 0.25 (or whatever matches the X scale). To avoid doing this for every section, only do one section, delete the others, then use paste special to paste the rest back into place (5 Y rot, 16 Y move for twistCorridor2). Unfortunately scaling 'breaks' the texture alignment.
Important! - These walls won't seal the map as there may be tiny gaps (due to floating point inaccuracy), so seal the area around them with solid brushes. I also strongly advise leaving it as a func\_detail.