When you do "sta-lock" it locks the extension in the switch, preventing people from making calls from the extension no matter where they move the set. It will not, however, prevent them from unplugging the phone and physically move it to a different location. If I understand you correctly, and there is a chance that I don't, I would disable ALL the ports that do not have phones connected to them. I do it in my facility, and the TTI code is a big "NO-NO" to everyone.