Announcements on the door

I juss had a thought....

There are alot of ways to alert people in this day of age

Walkie-Talkies
P.A. system
Text message
Phone call
Dry erase board

Anyway, i'm thinking of a way to communicate announcements on ur door
For example:
Prayer Room: Do not disturb
Sister's Room: Do not disturb


But how can we put signs on the door to let sisters know stuff
like their personal room, not for the other rooms

I was thinking, for each room there wud b a little dry erase board to write appts, chores, and other stuff on for each siter in that room, or each child and mom in that room.

How about sticky notes? (nah)
How abt Bullentin boards? (mini)

Good examples in which to use