On the House: Here’s a trick to keep things square
Published 12:01 am Sunday, March 13, 2011
As carpenters-turned-journalists we sometimes take for granted many of the tricks of the trade that we learned while working in the trenches.
Here’s a trick that we hope will help you complete your next do-it-yourself project more quickly, easily and accurately.
We all know that a square is an L-shaped, right-angle tool that is used to draw lines perpendicular to the edge of a given piece of material. There are small squares and large ones, but they are all basically used for the same purpose: making perpendicular lines.
A small square is used when marking a 2×4 or a 2×6. A larger square — known as a framing square — is used when marking larger material such as 2×10 and 2×12. There is yet a larger square — known as a T-square that is used for marking sheets of plywood, wallboard or other sheet goods.
Why is squaring so important? Simple; making a perfectly square cut is important if you want to build a project that won’t end up looking like the leaning tower of Pisa.
Well, if squaring is so important how can such a small tool be used to align foundations, cabinets and walls? Truth is a square is great for small work, but when it comes to aligning larger projects it’s square to use a square.
Here’s an example of what we mean: How would you use a square to ensure that a new 6-foot long wall will be placed at a perfect 90 degree angle to an existing wall? Carpenters use a simple trick known as “3-4-5.” Here’s how it is used:
•From the intersection of the walls draw a line/point along one wall exactly 3 feet from the corner.
From the intersection of the walls draw a line/point exactly 4 feet away along the other wall.
Measure the diagonal distance between the lines/points. When the distance is exactly 5 feet the perpendicular walls are perfectly square to each other.
By the way, the last measurement, the 5-foot diagonal one is known as the hypotenuse — the line opposite the right angle. Actually, it’s all a function of basic trigonometry known as the Pythagorean Theorem. It basically states that in any right triangle, the square of the hypotenuse is exactly equal to the square of each of the two legs in a right triangle. The formula is written as A2 + B2 = C2. Let’s try it out on our 3-4-5 trick:
•32 (or 3×3) = 9
42 (or 4×4) = 16
52 (or 5×5) = 25
The formula really works: 9 + 16 does equal 25.
Here are some uses for the formula:
•Square a framed wall to insure that it isn’t built as a trapezoid.
Square a foundation so that the structure will be square.
Square a peninsula cabinet so that a pre-fabricated top will perfectly fit.
When a carpenter installs a U-shaped set of cabinets they aren’t necessarily placed against the rear walls and fastened in place. The carpenter will loosely place the cabinets against the walls, lightly fasten the two inside corners at the face of the cabinet configuration and use the 3-4-5 formula.
With the cabinet faces square, the backs of the cabinets can be affixed to the uneven walls with shims. When the counter is installed its back edge can be fitted (scribed) to the walls — hiding any irregularities. Why all the work? Simple; 99 percent of the time, walls are wavy and crooked and you don’t want the face of your cabinets to mimic crooked walls.
By the way, it’s easy to determine if a four-sided shape (like a window opening) is perfectly square. Make opposing diagonal measurements. If the diagonal measurements are identical, the opening has four square corners and, in this example, the window can be installed.
Now you know that when it comes to construction, it’s hip to be square.
For tips from James and Morris Carey, go to www.onthehouse.com or call the listener hot line, 800-737-2474, ext. 59. The Careys are also on KRKO (1380-AM) from 6 to 10 a.m. every Saturday.
