A lock-out period usually applies to theatre events, and is a period after the commencement of a performance during which patrons will not be admitted to the auditorium. Any late-comers who arrive during this lock-out period will only be admitted at a suitable break in the performance. Some events may not admit late-comers until intermission or will not admit late-comers at all after the performance has begun.
The duration of the lock-out period varies between events and is set by the venue and promoter.