Now I have a laser level, but the tripod isn't tall enough for 7', so I needed another method to level the top of the posts. Inspiration, a water level. Looked online, found water levels ranging in cost from about $30 up. Figured I could do better and remembered seeing something years ago made from a water hose. Jumped on my motorcycle and off to the local lumber yard for parts. I bought one 3/4" female hose end and one 3/4" male hose end and 2' of clear 3/4" plastic hose. Total cost was just under $5.50, not bad.
At home, I microwaved a cup or so of water for 3 minutes, dunked one end of the clear plastic tubing into the water for 10 - 12 seconds, and pushed one of the hose ends into the softened tubing. Cut the tubing into 2 even pieces, and repeated the process with the other hose end connector. The tubing I bought was from close to the end of the roll, so it had major curve to it. I dug around in my junk and found a piece of lightweight U channel just big enough for the tubing to push into. Cut the channel slightly shorter than the clear tubing, and then shoved the tubing into the channel. It still wanted to curve, so I took a few zip ties and tightened them around the channel, starting in the middle, then doing the ends (this removed the curve). I did learn that it is best to place a block of some sort inside the channel prior to cutting it, in order to keep from bending it out of shape. Now to make it variable length, just use a longer hose, or connect two hoses. You need to make sure there are good washers in the female ends so water doesn't leak out and change reading. Mark one line on each piece of tubing for the leveling marks. Very simple build, took maybe 10 minutes.
Tools required, screw driver for hose ends, knife for cutting tubing, hacksaw for cutting channel (light weight angle would work also) and wire cutters for cutting the ends off of the zip ties.
If desired, add food coloring to water to make it show up better.