Perimeters are expansion patterns for trees of safeguards and security profiles (evl).
Some perimeters are part of the standard library. You may add your own ones,
The process is as follows:
1. Create a new label with a name you choose:
Expand > perimeter > new label
2. On the tree (safeguards or security profile) expand the tree as appropriate for your purposes.
3. Load current shape onto the named label
Expand > perimeter > load > your label
4. To change shape, repeat steps 2-3
To use a label
Expand > perimeter > your label
To remove a label
Expand > perimeter > remove > your label