If you have asymmetric objects, and in the library there’s just the left (or right) version, you can obtain the specular copy by yourself.
Once the object has been placed in the Layout, click the right mouse button on one of the object lines; select the command Mirror.
The Application needs you to specify the line that will define the mirror: in the following image it is the vertical, red line in the middle.
This line tells the Application how to mirror the objects.
Specify 2 points and you will obtain a new object, specular to the first one by that mirror line (you can click the first one where you want; then it might be important that for the second one you remain horizontal or vertical.
For this purpose remember that you can enable Orthogonal mood, by pressing O keyboard button)
This article is valid for DomuS3D® 2017 and later versions