Whether you're a professional carpenter or a do-it-yourselfer, a bubble level is a must-have tool. Also called a spirit level, this tool helps to keep your projects perfectly horizontal or vertical -- level or plumb. Commonly used levels typically have two glass tubes, one to determine level and the other for plumb. For most around-the-home projects, such as hanging pictures, installing a closet shelf or leveling an appliance, a 2-foot level is all you need. Once you've tested the level's accuracy, reading it is simply a matter of knowing what the bubble indicates.
Clean and Test
Examine the bottom edge of your level before taking a reading. If there's a buildup of dry dirt, cement, calk or a similar substance from a previous job you will not get an accurate reading. If the edge is dirty, wipe it down with a damp rag. For stubborn buildup, carefully chisel the substance off the edge and then wipe it clean.
Test the accuracy of your level. Hold your level lengthwise against a flat, vertical surface such as a wall. Slowly move the right end up or down until the bubble in the spirit tube is centered between the two lines drawn on the middle of the tube. Run a pencil along the bottom edge of the level to draw a line on the wall.
Flip the level over so that the top edge is now the bottom edge. Put this edge on the line and look to see if the bubble is centered between the lines of the tube. If it is not, the level is defective and should not be used.
Read for Level
Set the level on the surface of the object you want to check for true horizontal or level. The spirit tube should be parallel to the surface of the object. Allow the bubble to the float and settle in the tube.
Move close to the level and position yourself at eye level with the tube. Close one eye to get an accurate reading. Take note of where the bubble has settled in relation to the lines drawn on the tube.
Make a reading. If the bubble is perfectly centered between the lines, the object is level. If any part of the bubble is right of the right line, the object is slanted or slopes downward from right to left. The object is slanted or slopes downward from left to right if any part of the bubble is left of the left line.
Read for Plumb
Hold your level vertically and place it against the surface of the object or surface you want to check for true vertical or plumb. The spirit tube should be perpendicular to the object. Allow the bubble to float and settle.
Move close to the level and position yourself at eye level with the tube. For an accurate reading, close one eye. Take note of where the bubble has settled in relation to the lines drawn on the tube.
Make a reading. If the bubble is perfectly centered between the lines, the object is plumb. If any part of the bubble is left of the left line, the top of the object is tilted and leans to the right. The top of the object is tilted and leans to the left if any part of the bubble is right of the right line.