Cutting Walls

What am I missing? I’m trying to create wall openings for ducts. I’m able to get the ducts from a linked file, and identify where they intersect with walls, and identify the ducts centroid. What I can’t seem to do is actually make the opening in Revit - and thoughts?

We are doing it this way:

Hosts are the Walls,
Type is a Wall-Opening / Cutting Family
Points are the clash centerpoints


Hi, @paul.davis
The problem with Familyisntance.ByPoint in this case is that it places the family instances by (not surprisingly) the points. And to cut through the wall the wall needs to be hosting the void as shown in the example by Johannes.