You can draw square areas on the tiled floor or walls of the project, when you are in the Navigation window (or in Wall window as well). Click the right mouse button on the wall you want to refer to, and select command Tiles layer. You will access the mask where to specify the size of the square you want to add to the wall:
Finally you will locate the area on the wall, as you can see in the next image (the insert is the grey square rundd with a red line, under the mirror).
This article is valid for DomuS3D® 2017 and later versions