Every badge at the Harbourline Forum carries a strip of five letters along its coloured band (sample).
A is the Main hall, B the River room, C the Workshop studios, D the Market floor and E the Forum dinner in the Grain Store. A solid letter is a room your pass opens; a dashed one is a room it does not.
The stewards on each door read the strip, so you never need to show an email or a printout. If your plans change, the ticket desk can upgrade your pass and print a new badge in a minute.