A-page
Also: A-pages · star page
An A-page is an inserted page in a locked shooting script that adds material without renumbering the pages that follow. When new content lengthens page 12, the overflow becomes page 12A (then 12B, and so on), so page 13 keeps its number and every department's existing references stay valid.
Once a script is locked, page numbers are as fixed as scene numbers. Adding half a page of new material cannot be allowed to push every later page number forward, because that would invalidate every schedule and breakdown downstream.
The fix is the A-page: the addition lands on 12A, leaving 12 and 13 intact. The same logic that produces 47A scene numbers produces 12A pages — both are how a frozen document absorbs change without disturbing its addressing.