We do not have to create all 3D surfaces. If an object is symmetrical, exactly the same on both sides, we only need to build one side and then simply specify that the other side is mirrored. This saves a lot of time.
Note that this is a software feature, not hardware. It is found in some (but not all) 3D modelling tools.
3D Kit Builder
To remove mirrored surfaces from our example 3D Kit Builder model use the following Display options: