Office hours are posted for mutual benefit. I ask that students respect them. If you need to see me outside of office hours then I ask that you observe the following door codes:

Door Open -- ask to come in, I probably have some time
Door Cracked -- I am probably in a meeting, on the phone, or working on something that demands immediate attention. It is unlikely that I will be able to see you.
Door Closed -- Check the schedule. I am probably in class or away from the building.

If I am in the building, my office door is normally open. In addition, students needing to see me outside of normal office hours can make an appointment.