# Planar clipping/merge with Mirror modifier

I am looking at work-flows for building roofs. Below was promising until I hit a snag...

### Setup

1. Rotated Plane + Mirror modifier.
2. Alt+Space (Transform Orientation) > Normal
3. Ctrl+Alt+Space > Create Orientation for sloped plane
4. G, X ...
5. When the two planes meet, they 'climb' up the global Z-axis, which I don't want (below)

### Question

How do I constrain the merged verts to the selected Orientation (i.e. staying in line with the roof?

• Why not using Clipping option of Mirror modifier ? It won't anwer your question, it should prevent that situation. – Mr Zak Jun 30 '15 at 10:34