I literally knocked one of these up in 45 mins from scrap pieces I found lying around, the most time was spent making a 'safe' plumb bob on the advice from Ralph. I used a cut down 3" nail, put a new point on the end and filed the tip to remove the sharpest bit of the point, the light weight combined with a blunt tip ensures it will not damage even the lightest covering, I then used thick (saddle) thread for the plumb line. I think that's the biggest mistake people make when putting one of these together: they make the plumb bob too sharp and too heavy because the line they use is too thick. It doesn't need to be.
Stay low, Move fast, Trust no-one....
