When editing the structure of a vertically compound wall, use the Merge Regions tool to merge wall regions (or layers) together horizontally or vertically into new regions. Highlight a border between regions and click to merge them.
To access the Merge Regions tool, open the Edit Assembly dialog for the wall type. See Access Tools for Vertically Compound Walls.
When you merge regions, the position of the cursor when you highlight a border determines which material prevails after the merge.
The material from one region prevails when you merge