This month's topic is squares. Along with marking and measuring gauges there have always been some form of squares. From something small enough to fit in your pocket to a large drywall square over 48" long and 24" wide. I've grouped them into five sections; Rafter, Try, Combination, Angle, Protractors & Special Purpose. This should cover the majority of squares and help you decide what you need.

Rafter-Carpenter Squares
These square are probably the most recognizable, but most underused square available. One side is 24" long by 2" and the other is 16" by 1-1/2" set at 90 degrees. This provides you with the two standard stud spacing distances as well as stud width. Dimensional markings are on both sides with 1/16" on one side and 1/12" and/or 1/10" on the other. In addition to this, they are marked for octagonal scale, board measure in 1/100ths and have etched rafter tables. These tables are often over looked by most people and they can be very handy. Take the time to learn how to read them and you will be able to cut rafters without having to measure for each one. You cut one to length and then find it on the chart. It tells you the length needed at the next 16" spacing. Metric squares are also available. There are smaller versions available with 12" x 1-1/2" & 8" x 1" arms or 8" x 1-1/2" & 6" x 1" arms, but these sizes do not have the tables and added information on them. Knurled knobs are available which help in laying out stairs.

Try Squares
These squares, like rafter squares, have two arms at 90 degrees to each other. One arm is steel or aluminum and can be 6" to 12" long with or without markings. The second arm or body can be of plastic, wood or metal. The body of some squares is clipped at 45 degrees so the square can be used for marking mitre joints. I prefer squares with markings as it saves a step and the body material is more an issue of durability and feel. When buying a try square there is one main thing to check and that is making sure it is 90 degrees. A quick way to do this is to set the square against an edge you flat and straight. Make a mark, then flip the square over and see if the mark will still line up. Two sub-categories of Try squares are machinist squares and speed squares. Machinist's squares are all steel squares with no markings. Blades are hardened and machining & accuracy is of a higher grade. Sizes range from 4" to 12". Speed squares are a relatively new square whose popularity has really taken off. The reason they are so popular is because they are so useful. Made out of plastic or cast metal they are shaped in a triangle. One side has a raised rib, which is set against the material and you can quickly mark 90 or 45 degrees, or because of the markings, any angle in between. They come in two sizes, 7" and 12".

Combination Squares

These squares have a steel ruler with either a groove or slot, which the body of the square rides on. The body can be plastic or cast and is designed for 90 and 45-degree angles. Most have a level vial and a pin used for marking built into the body. Like the Try square the most important thing is accuracy. Check how well the body tightens down on the ruler and how much play there is. They are available in imperial or metric or both. Some squares come with two additional attachments. One is a compass dial/protractor head so you can mark any degree needed. The second is a center finder head set at 45 degrees to the edge of the ruler.

Angle Squares
These are squares with movable arms. One being the sliding bevel the other is often called a layout square. Readers of Hand Tool Basics #5 may remember a section on the sliding bevel under measuring gauges. I don't know why I put them there other than it seemed a good idea at the time. Sliding bevels have a body of plastic, wood or steel and an aluminum or steel blade. The blade has a slot in it and attaches to the body by a lock nut or knob. The blade pivots to any angle and is excellent for transferring angles, especially from existing furniture or material. These squares are not normally marked but there are some, which have imperial or metric etched into the blade. They were also traditionally used in marking dovetail angles. When buying a bevel, check that the locking mechanism secures the blade snuggly. You don't want one, which will change angles with only slight pressure. The layout square looks like a triangle of steel or aluminum and has a movable, locking arm. The arm can be set from 0 to 70 degrees. There is also a mitre square, which has a steel blade with a wooden or steel body set permanently at 45 degrees.

Protractors & Specialty Squares
Protractors combine a compass dial with straight edges. They allow you to set and mark angles and in some cases act as power tool guides. The more basic ones can be set to single degree and some of the better ones can be set to the half degree. Sizes ranges from 6" to 20" and material can be plastic, aluminum or steel. They are usually very reasonable priced and for myself I find it handy to have a small one and a large one to fit the size of the project. Drywall squares look like oversized drafting T-squares. They are designed specifically for cutting straight edges on a sheet of drywall. The body arm sits on top of the sheet and the 48" measuring arm extends down the side. Some are permanently set at 90 degrees others are adjustable.