American professors hold office hours, fixed times each week when students can come to their office. At California State University, Long Beach, policy requires one regularly scheduled office hour per week for every three weighted teaching units taught, up to four hours. The hours must be posted by the office door and listed on every syllabus.
The policy adds that the required hour “cannot be met, entirely or in part, by stipulating ‘by appointment only.'”
Even the time for dropping in is a fixed slot.