Carpenters have an understandable hang-up with angles; which sort of explains all the references to "plumb" and "square" in any literature on the topic. To be certain, the carpenter's squares - framing, try, speed, combination - are all designed in the hope that every corner will be a perfect 90º right angle. The truth is, of course, that right angles are an ideal, but not necessarily a fact, and having to deal with non-square corners and oddball angles is a fact of life.

So, whaddya gonna do when you run into one of those corners that aren't square, especially when you have to built something that fits into it? You're going to pull out your Sliding T-Bevel Square, in my case a Sears Companion Square model 39582 - and you're going to copy that angle to your workpiece. It's that simple.


You see, unlike other kinds of squares, a Sliding T-Bevel doesn't have two arms fixed at 90º from one another. Instead, the t-bevel square's two arms are connected by a pivot so that they can be opened or closed at any angle from one to 180 degrees. There's a fixed arm (the stock) made of wood or plastic - in the case of the Companion 39582 it's made of high-impact plastic - and the other arm is a narrow metal blade (the tongue). The tongue is captive to a pivot that's fixed in the top of the stock, with a thumbscrew on the pivot so the tongue can be locked in place by friction. The tongue can be extended into a letter L shape or shortened up to form a T. When not in use, the tongue rotates into the stock to form a compact I shape for easy storage.

To use a sliding T Bevel Square for copying angles, simply loosen the thumbscrew, open the tongue so that the two arms match the angle, and re-tighten the thumbscrew. With this version of a T bevel, you can loosen and tighten the locking screw one-handed while your other hand steadies a workpiece, holds the square in place, or clings to a ladder for dear life. Once you've copied (and, of course, verified) the angle, you can then either measure the angle with a protractor or just copy it to your piece of molding or other lumber with a pencil. A little work with a standard compass (in the geometry-class sense, not the orienteering sense) will let you bisect the angle for cutting miter joints to fit non-square angles. If you already know the correct angle, you can use a protractor or even a speed square to set the angle between tongue and stock, then transfer it to your workpiece.

Most Sliding T Bevels, including the Sears 39582, have a 45º cut across the tip of the tongue, which makes marking standard miter corners easier. Almost all - if not all - versions have a finger groove in the stock to make them easier to hold.

High-end versions of the Sliding T-Bevel Square have riveted hardwood stocks with brass fittings and stainless steel tongues, occasionally even wooden tongues. The tongue length varies from eight to ten inches (this one has a nine-inch tongue) and occasionally as much as eighteen inches in length.


A Sliding T-Bevel Square will prove invaluable to any carpenter or handyperson who finds the need to reproduce non-square angles. This is one more inexpensive, basic tool that should be in any homeowner's arsenal.



Note: another relatively inexpensive tool that can be very useful for determining angles, especially on large surfaces, is an angle finder. Guess what: I have one of those, too...


Recommended: Yes