I don't know how it is now but the assistant stage manager had to understudy several parts. You had to be ready to go on at any time if the actor couldn't make it to the play. I didn't think anything of it.
“Every now and then I have to teach directing. The thing about the theatre is that the most important thing you can do as a director is to make sure that everybody is in the same world - you have to create the world and make sure everyone buys into it.”
“Taking stock of what you own, when done correctly and thoroughly, helps dampen the urge to shop frivolously.”