feeling a bit off axis? build this level out of a couple of nuts and bolts, clear tubing, and olive oil.
Step 1: Parts Layout
+ a few inches of clear plastic tubing (3/8" inner diam., 1/2" outer diam. ~2.50$/roll @ homedepot)
+ two matching nuts and bolts that fit snuggly into clear plastic tubing. (7/16" worked well)
+ drill bit big enough to send string through (1/4" is fine)
+ a few nails
+ hot glue
+ olive oil (or any liquid, really; i chose olive oil for it's colour and viscosity)
+ a piece of wood that you feel is level (and pretty).
Step 2: Assembly, Pt. 1
Place a nut onto the bolt. put some hot glue on the end of the bolt and put the bolt into the plastic tube. The bolts must be able to seal liquid. a snug fit + hot glue should do the trick.
Step 3: Assembly, Pt. 2
put some oil into the glass tube. You want to add just a litle less oil than will completely fill the tube after the next bolt goes in. Eyeball well, and then pay attention to how deep you add the second bolt. The excess air in the tube will be the air bubble that makes the level useful.
Step 4: Assembly, Pt. 3
put a nut on the second bolt, put hot glue on the tip, and insert into the tube. now, the leveling mechanism should be complete, ready to be attached to the base.
Step 5: Assembly, Pt. 4
get your level piece of wood and eyeball where-abouts you want to attach the leveler. drill holes in the wood so that you can loop string through to tie the bolts down. A nail next to each set of string-holes will be helpful, too.
Step 6: Assembly, Pt. 5
tie down the bolts by sending string through the holes and around the wood + bolt. Then wrap the string around the nail, kind of like a guitar string around a guitar peg. Make sure the the bolts are level - a flat face of the end of the bolt and the nut on each bolt should both be in contact with the wood. If both bolts have flat sides touching the base plate, and the same buts and bolts were used, then the device should be right about level.
The string goes through holes in the mid scetion of the wood in order not to disturb the flatness of the bottom of the wood base plate.
As you are tying, the air bubble in the tube should be roughly centered in the tube. If this isn't the case, check that the bolts are the same and level. Another common problem is that the tubing is bent, and thus not level. Use a smaller gap between the bolts to encourage a flatter tube. Also, check another level, because maybe the table you are working on isn't level.
When your done, use a permanent marker and mark on the tube where the edges of the air bubble should be when the device is level, for reference.