[Chimera-users] join models

I cannot for the life of me get join models to work. 1. I have two structures. 2. The structures overlap. 3. I align them using matchmaker. 4. I delete the overlapped residue from one chain. 5. I select the appropriate C and N terminal residues 6. I try to use join models under Build structure 7. The apply box remains gray, no matter what residue or atom I select. What are common problems that cause join models to not work? Stewart Morley Brigham Young University