This article is from the Theatre FAQ, by aku@leland.Stanford.EDU (Andrew Chia-Tso Ku) with numerous contributions by others.
Cancellation lines sprout when a show reaches sellout status. The
term "cancellation line" is a bit of a misnomer, because most of the
tickets sold this way are actually house seats reserved by producers
to give to VIPs, and are only sold to the public at the last minute,
just before the curtain rises. These seats can be very good indeed,
but the possibly of not getting in (the number of available seats
isn't announced until the last minute) can deter many. Tickets are