Here is another version, made mostly from recycled materials. Two pieces of aluminium (correct Australian spelling) tubing, a piece of coat-hanger wire, a piece of EPP packing foam and a piece of venetian blind cord to make the basic rig. I found a plumb bob in my nuts & bolts bucket in the garage (but you could use a pyramid shaped lead fishing sinker or anything similar).
Method:
1. Cut tube to desired length (length is not important).
2. Drill small holes in one end to tie string through, drill correct size holes for dowel to freely turn at other end.
3. Bend coat-hanger wire around dowel to form the hook to hang plumb bob from
4. Push a piece of EPP foam into the fat tube at the end where the dowel goes. The EPP foam works as a friction brake on the dowel, no need for a cinch bolt.
5. Push a pencil or similar through the foam to where the dowel goes through.
6. Cut a small slit in the foam to slide the hook into and slide hook in from bottom.
7. Push dowel through the dowel hole with foam and hook in place.
8. Tie small loop at top to hang rig from.