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The block aligns itself to the wall, and cuts the opening. 
- Drag more blocks onto the walls. The block will change its alignment to fit any wall.
Note: This tool only creates rectangular cutouts, even if the block is non-rectangular. You can change this by modifying the block. See Edit Opening Modifier.In Plan view, the openings are represented by the 2D block. 
- If you assign the 3D block a material such as glass (in the 3D page of its Properties), and assign a brick material for the walls, you can see the results in render mode.
