Two measuring squares (top and right), as well as combination square and try square (bottom left).
Traditionally, the larger metal squares like the rafter square were thought of as carpenter's tools. In contrast, smaller wooden or metal ones were more likely to be found in the joiner's or cabinetmaker's tool kit. However, that line was blurred many years ago and today the well-equipped woodworker of almost any stripe finds many uses for both large and small squares.
Hand squares have been used for most of recorded history. Many handmade squares survive from earlier eras and, in a sense, the handwork ethic is still honored; even today, hand squares are more likely to be crafted of expensive woods and admired as much for their ornamental appeal as their practicality.
I've included several distinct varieties under the heading of hand squares, including the try square, the measuring square, and the combination square.
Try Square. A fixed ninety-degree angle is formed by the thin steel blade and the thicker stock, which is often made of wood. The try square is used for checking (that is, "trying" thus the name), for establishing that a cut or joint is true or square. It's also used to mark cutoff lines or as a straightedge to determine whether a board has warped or "cupped".
Try squares come in a range of sizes, with blade lengths varying from two to twenty-four inches, depending upon the age of the tool and the purpose it was intended to serve. Machinist's or engineer's try squares are made entirely of metal and are smaller in scale.
The try square is typically put to use in this way. Lay the tongue flat upon the work piece, then slide the stock flush to the edge of the wood. Thanks to its thinness, the tongue can then be used to scribe an accurate line on the piece to be cut or shaped. Try squares, both new and old, are often tools of great beauty, with blades of fine steel, iron, or brass, with stocks or rosewood, ebony, or other hardwoods. The blade and stock are sometimes fastened together with decorative rivets.
Measuring Square. Sometimes called a "magic square," angle square, or protractor square, this tool functions as a square but is shaped like a triangle. One leg of the triangle has dimensions marked on its face in inches; the other has a raised ridge on the top and bottom to allow it to be butted to the work piece. The third and longest side of the right triangle, the hypotenuse, has degrees (zero to ninety) marked on it to help in measuring and marking miter cuts.
Made of cast aluminum, the measuring square serves most of the same purposes as the try square: You can use it to check a cut or joint for square, to mark cutoff lines, or as a straightedge to identify warped or cupped boards. The magic square is also handy as a cutting guide when using a hand-held circular saw.
The measuring square is available in two sizes. The smaller size is seven inches on a side (the hypotenuse is just under ten inches), while the larger version is twelve by twelve by seventeen inches (actually, for sticklers who know the Pythagorean theorem, the precise measurement is 16.97 inches). The smaller magic square fits comfortable into a pocket of most tool belts.
The larger model is especially handy when working on large dimension lumber, two-by-eights and up. Its size makes it handy for laying out framing, when transferring measurements from one wide piece of lumber to another.
Another application for the larger square is in laying out rafters and stairways. An attachment called a layout bar is bolted to the under side of the square, and can be fixed at certain angles (or pitches) for speedy marking of plumb lines or bird's-mouths on rafters or riser and tread cuts on stairs. This handy extra turns the measuring square into a sort of bevel gauge (see page 21), with one angle preset so that it can be quickly and accurately marked and replicated.
Like the rafter square, a measuring square purchased new will come with an instruction booklet that contains rafter tables and explains a variety of techniques for which the tool can be used.
Combination Square. This tool is essentially an adjustable hand square, with a couple of clever advantages.
It consists of a rigid steel rule, usually twelve inches long (though sometimes combination squareshave rules up to twenty-four inches in length. A knurled nut and set screw are used to fix the headpiece to the rule at any point along its length, depending upon the purpose to be served. The headpiece has both a ninety-degree edge and one that forms a forty-five-degree angle with respect to the rule. The fort-five-degree angled edge accounts for one of the tool's alternate names, the forty-five-degree miter square. It's ideal for marking (and checking) both ninety-degree crosscuts and miter cuts.
The purposes vary: The combination square can be used as a try square, to determine the squareness of a piece of joint; like the measuring square, it can also be used as a saw guide. When the head is set at the end of the rule, the combination square can measure heights. It can also be adjusted to measure depths, and some people find it's handiest for marking.
There is a spirit (bubble) level in its handle, so the combination square can be used for leveling. Some models even have a scribe in the handle.
Not all combination squares are created equal. They range in cost from about $15.00 to as much as ten times that price. The most expensive models come equipped with two additional parts: a protractor head, for marking and measuring angles, and a center head, for locating the center of a circular or cylindrical work piece. But it isn't the added elements that account for the higher price.
The explanation is that the best combination squares are precision tools, useful for accurate work requiring tolerances beyond those needed by most woodworkers. However, if you work involves pattern-making or machine makereadies, for example, a more sophisticated combination square may prove to be a wise (even lifelong) investment. A top-quality square will stand up to lots of abuse without losing accuracy.