Levels

In making or repairing small rectangular objects, a square is invaluable in helping ensure the joints are tight and the overall shape is true and square. But for a fixed structure, the scale of a mere square, even a framing square, doesn't permit it to provide all the answers.

Enter the level and its partner, the plumb. These tools are used to establish true vertical and true horizontal.

The key element in a level is the sealed glass or plastic tube containing water, alcohol, chloroform, or some other clear liquid. The tube or vial is slightly curved and has two parallel lines drawn at its center. The vial is nearly filled, leaving an all-important air bubble. The vial is then precisely mounted in the body of the level.

No matter what size the level, its function depends upon that tiny air pocket in the vial. Since the specific gravity of the fluid is greater than that of air, the bubble always rises to the highest point in the vial. When the frame of the tool is precisely level, the bubble will be aligned between the two hairlines at the center of the vial.

The bubble tube or vial can be mounted in a variety of instruments. Some are fixed permanently in place at the time of manufacture, others are adjustable or replaceable. the most common kinds of levels are described below:

Carpenter's Level
These levels come in many sizes, as two-, four-, six-, and eight-foot models are commonly available. For the tasks most of us address, one each of the two-foot and four-foot varieties will be sufficient.

Two-foot levels consisting of a wooden body and one or more bubble tubes are generally called carpenter's level. Typically, such levels are about three inches high and an inch or so deep.

Two-foot and four-foot models alike usually have three bubble vials, one at each end mounted transversely for establishing true vertical, and one mounted at the center along the length of level for horizontal leveling. For generations, carpenter's levels have been made of handsome (and very stable) woods like rosewood, ebony, and mahogany.

Mason’s Level
Mason's levels are usually four feet or longer. Two things to keep in mind: the longer the level, the greater the accuracy — and that when working in cramped quarters, an overlong level is useless. So having a nine-inch torpedo level in your kit is probably a good idea. There are smaller one, too, as short as an inch in length.

For odd jobs around the house, the two-foot length is easily stored, and used. The four-foot level is handiest for cabinet installation.

Vials are replaceable in many new models. Some levels also have a vial set at a 45-degree angle to the length of the tool. This allows you to determine proper position for braces and other angled pieces.