Let's say you go to their camp and your friends aren't there. You want to leave a note, but, alas, you have no paper, pencil or way of keeping the paper from flying away in the gusty, dusty wind.
Well, there are no worries if your friends were smart enough to use chalkboard paint to paint the perfect place to leave a note and not have it blow away!
We decided we'd repaint the dark brown stripes on our ancient motorhome with chalkboard paint. The old stripes were pretty deteriorated, but we just washed the area, let it dry and applied 3 coats of chalkboard paint (available at most home improvement stores and craft stores.) The paint drys really fast and then needs 4 hours to cure before using (though your paint's directions may vary.)
We'll put chalk in a bag attached to the door handle.
We'll also be able to leave notes for each other, the day's food menu, job assignments,etc. This is the mothership and our little group is mostly camping in tents.