In the beginning, there was the Committee. And the Committee decreed that there shall be a Door Group. Or something like that.
Door members are simply normal people who are trusted with the responsibility to unlock the clubroom and to allow other people to use the room in their presence. Door members also get access to the tool cupboard, machine room and vending machines via the keys in the lockbox.
Any ordinary club member can apply to be added to the Door Group ("apply for door"). This is fairly simple and simply involves sending an email to mailto:email@example.com with an explanation of why you want to be on door and a summary of your understanding of the Club Regulations (mostly just the Door Group bits).
Door Group Manual