When editing , use the Split Region tool to divide a wall layer (or regions) horizontally or vertically into new regions. When you split a region, the new regions assume the same material as the original.
Horizontal split preview
After you split a region or layer horizontally, click the border between the regions. A blue control arrow displays with a temporary dimension. If you click the arrow, it switches the constraint and its temporary dimension between the top and bottom of the wall. See .
Blue control arrow displayed when border is selected
Vertical split preview