Scene numbers
Also: locked scene numbers · scene numbering
Scene numbers are the figures placed beside each slugline in a shooting script so every scene has a stable address. Once a script is "locked," these numbers never change: new scenes get letter suffixes (47A) and deleted scenes are marked OMITTED, so the whole crew keeps referring to the same set.
Before production, scenes are simply in order. At lock, they are numbered and frozen. Locking matters because dozens of departments build their own paperwork — schedules, breakdowns, call sheets — keyed to those numbers.
After lock, you cannot renumber. Insert a scene between 47 and 48 and it becomes 47A; cut scene 47 and it becomes "47 OMITTED." This preserves every existing reference while still allowing the script to change.