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“Binding” means: which node of the design does this rule attach to? This is controlled by
the rule’s Level, and it is where most confusion (and most bugs) come from.
The assembly hierarchy
Every unit is a tree of nodes, each at an assembly level:
| Level | Node |
|---|---|
| Overall / Facet | The whole unit and its major faces (top of the tree). |
| Frame | The fixed outer perimeter. |
| Opening | A hole within a frame. |
| Mullion / Coupler / Divider | A bar that splits an opening or couples openings together. |
| Sash | The (often operable) panel that holds glass. |
| Shape | The drawable opening shape itself — e.g. a door leaf or a fixed lite. |
How a rule says “attach me here”
A rule carries two pieces of level information plus an ancestry path:
- Level — the level of the node the rule targets. The rule only matches a node at exactly
this level. - Parent level — a secondary qualifier describing the node’s context (what it sits
under). It steers some downstream behaviour, especially for machining notches. - Ancestry path — the chain of parent levels above the target, so the same level under
different parents can be told apart. Empty slots act as wildcards (match anything).
The Level dropdown sets BOTH level and parent level — together
In the rule editor there is no separate “parent level” field. When you pick an entry from the
Level dropdown, it sets the level and the parent level as a matched pair. So two entries
that read alike (for example, the same shape but reached under a different parent) will bind your rule
to different nodes and can produce different geometry. When a rule works on a plain unit but
goes wrong on a variant layout, suspect the Level first.
In the rule editor there is no separate “parent level” field. When you pick an entry from the
Level dropdown, it sets the level and the parent level as a matched pair. So two entries
that read alike (for example, the same shape but reached under a different parent) will bind your rule
to different nodes and can produce different geometry. When a rule works on a plain unit but
goes wrong on a variant layout, suspect the Level first.
This is exactly the trap in the worked example below: four “identical”
machining rules differ only in the Level they were authored at, and that alone sends the notch to the
wrong side.