As requested by arathea, dorm-doors can now be remotely claimed/locked/unlocked/unclaimed. No more sims running 5 miles uphill, against the wind both ways, in a blizzard to get to the desired room: simply claim your spot while still standing by the mail-box
Pause your game, select each sim in turn and have them claim their room. Then unpause for a moment, pause again, and you can all have them lock their rooms REMOTELY (if you don't want dormies to set up camp there). An hour sim time is now MORE than enough to house them all.
Be aware: once the Dormies start pouring in (after one sim hour), they have the same remote ability!