Re: Seeking a level using water and plastic tubing
It's called a water level. You have a vessel of water set at a fixed height. To that vessel you connect a length clear tubing. The other end of the tubing is connected to a story pole (yard stick ). The length of the tubing will depend on the distance you're trying to cover.
Once everything is set up, start at one side and note the water level in the tubing, move along the length of the wall to find the high/low points, then determine where you wish to install your chair rail.
IMHO, this isn't a necessary step for your chair rail because you want the rail to be a certain height from the floor, not necessarily perfectly level. To do so would draw attention to the unlevel floor with a "crooked" rail.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!