• Keeping molding level is very important.Jupiterimages/Comstock/Getty Images
  
  When installing crown molding, it's critical to ensure that it is level with the floor and ceiling. Just a tiny irregularity could result in molding that is crooked by several inches once it reaches the end of a long wall. Many tools exist to help you make sure that your molding is level.
  
  

Traditional Level

• A traditional level is a long piece of wood or metal containing a glass tube filled with liquid. The tube contains a large air bubble and is marked with two lines. To use this level, place it horizontally against the wall and shift the ends up and down until the bubble is centered between the two lines. The level can then be used as a straight edge to mark a perfectly level line along the wall.
  
  

Digital Level

• A digital level looks the same as a traditional one, but instead of a tube, there is a display panel that tells you the angle that the level is resting at. Adjust the ends up and down until the reading is 0. As with a traditional level, you can use the digital level's edge to draw a straight, even line.
  
  

Water Level

• A water level is simply a clear, flexible tube filled with water. It takes advantage of the fact that water will naturally stay in the center of the tube.. To use it, measure and mark the starting position of the crown molding. Hold one end of the tube with the water line even with the mark. Position the other end a few feet away, then raise and lower it until the water returns to the level of the mark. The water level on both sides of the tube are now exactly even.
  
  

Chalk Line

• Chalk lines are among the easiest leveling tools to use. The same distance is measured from the ceiling in two spots. A chalk-loaded string is stretched between the two points, and is then snapped against the wall to deposit its load of chalk. The chalk line can be used to install level crown molding, then washed off when it is no longer needed. Most chalk line tools have an internal chalk reservoir and a crank that lets you reel the string in when not in use.
  
  

Laser Level

• A laser level combines the technology of either a traditional or digital level with a laser beam. They are mounted on tripods and leveled out before projecting a beam onto the wall. Laser levels are available with multiple beams for corner angles, and even with rotating beams allowing you to mark the entire room at once. At the time of writing, these are the newest technology in leveling and are thus the most expensive.