You can assess either the face side (above) or the face edge (below) with an accurate wooden or metal straightedge.

Shop-made winding strips are the only means we have for assessing planar accuracy - in other words, twist.

A try square can be used for assessing right angularity (top) or as a layout tool for scribing a 90° angle (right).

Variations of try squares abound, from all metal or metal and wood styles (top left) to combination and adjustable stock options (below) to inexpensive “speed” squares (top right).

Miter squares, foreign and domestic. Another gift from the machinist’s tool bag.

To use a miter square, position your marking knife in the line on the face of the workpiece, then slide the miter square to the knife.

Three types of sliding bevels.

To use a miter square, position your marking knife in the line on the face of the workpiece, then slide the miter square to the knife.

In this lesson's goal statement, notice that the term "assess" is used instead of "measure." Here's why: with the exception of rules, measuring tools are actually limited to telling us when a thing is right. When it's not right, they don't measure by how much, just the assessment that "it ain't right." Regardless of skill level, we all face the same measuring challenges in our work. Therefore, every woodworker should have at least one of all of the following tools in his or her toolbox:

Straightedge

A straightedge is used to assess straightness or flatness. Originally shop-made, it has been replaced by a metal version. The bevel edge type is preferable because the narrower the contact face of the straightedge, the easier it is to see any inaccuracy in the workpiece. Straightedges come in different lengths with square or chamfered edges. They're not cheap, but they last a lifetime. It's the one tool you should "hand on" in as good a shape as the day you bought it. Don't use it as an edge to cut against because it's too easy to remove a sliver of metal from the straightedge with a misdirected marking knife.

Winding Strips

Twist is referred to by the woodworker as winding. A board or assembly in winding has its ends twisted in opposite directions. To check for twist, you need a set of winding strips. They are the basis for measuring planar accuracy - there is no alternative. Winding strips come as a pair of parallel-sided straight pieces of wood of the same dimension. They are not commercially available, so you make your own. The preferred wood for measuring tools, Cuban mahogany, is long gone. However, new Honduras mahogany will do fine. If unavailable, any clear, straight-grained, quartersawn and dry material will work. Make several pairs to the dimension that suits your type of working. Mark the centerpoints of each one with a sharp reference mark.

Check for twist by putting winding strips at each end of a board and at right angles to its length. Align your eyes with the center marks. Since half the board may be twisted and the other half flat, complete the survey by moving the winding strips closer together to determine where winding begins.

Try Square

A try square is used to assess right angularity. To "try" means to apply a test to determine whether a standard is met, and the standard here is 90°. Originally shop made and all wood, they are now manufactured with a wooden stock and metal blade or as an all metal engineer's square.

A popular alternative is a combination square borrowed from the machinist's toolbox. The part you hold is called the "stock"; the part at right angles to it is called the "blade" - though of course it doesn't cut anything. A try square can assess three 90° angles in your work: the inside edges of the stock and the blade, the outside edges of those same parts and the inside edge of the stock with the outside edge of the blade.

Combination squares have two features not associated with a try square. First, the blade is graduated so that it works also as a rule. Second, the blade slides. With these differences come new capabilities, but the difference extends beyond these because the usual 12" blade can be replaced by a 24" or 36" blade. Then again, any of these blades can have a revolving head or a 45° head attached to it instead of the usual 90°. It's these features that make it a "combination square."

There are also try squares with moveable heads and shorter 4" or 6" rules. The stocks are square and useable from either side, which is an advantage over the combination stock.

Finally, there are polypropylene "speed" squares that aren't altogether a try square, but they warrant inclusion because you can check an edge with them. They're cheap, lightweight, durable and resilient.

Miter Square

A miter square is used mostly for measuring and marking corner miter joints, which means that it's often only operating over a distance of 3/4" or so. The machinist's square and the wood-and-metal type are good for checking miters because you can offer them to the work like a try square. They are less good for marking out because you have to position the marking knife by deciding where you think the miter will fall by positioning your knife on the top edge - there is no assist. The Japanese miter square is very good for marking out because of a lip that hooks onto the workpiece. Put the point of your marking knife in the knifeline on the face of the workpiece and hold it at right angles. Slide the miter square up to it and it's accurately positioned to knife the miter line.

Sliding Bevel

On a sliding bevel, the blade is adjustable to the stock so that it can be locked at any angle. It's an essential tool in the marking of the tail piece of a dovetail joint and tenons with sloping shoulders. It's also useful for transferring an unknown angle from one workpiece to another. You can buy them made from wood and metal or all-metal construction.