If you are building a larger geometry you may find it convenient to create it in smaller pieces and then assemble them into the whole. Property sets make this easy, and they allow you to name the smaller pieces for convenience.
Property sets are used to bundle a set of geometrical objects in a group. The group is identified by a name. Typically a property set is used to mark subregions with share the same material properties or to mark portions of the boundary. For efficiency, the Design class object assigns a integer to each of its property sets, a so-called tag . The appropriate tag is attached to the elements at generation time.
See the file pycad/examples/quad.py for an example using a PropertySet.
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