From the Birchmere FAQ..I'm not sure this answers the question though..
6) What is the Flex Stage?
The Flex Stage is the area where we have dance-oriented shows at The Birchmere. There is a large dance floor in front of the stage, and there are usually NO tables or chairs in the room. Most Flex Stage shows are All Standing.
All Standing shows are indeed , ALL STANDING, which means there will be no tables or chairs in the Flex Stage (except for Handicapped Accommodations). For most All Standing shows, we will have the Music Hall open for food & drink.
Venue doors open at 6pm for Flex Stage shows, at which time entrance is completely general admission, first come first served. The Box office will be open at 5pm, but entrance will not begin until 6pm for all Flex Stage shows, and 8pm for ?Late Shows.? Line Numbers are not used for Flex Stage shows.