There are a few well known processes for squaring an object among the many different trades. But for the average guy who is starting out learning welding and fabrication, might not know these things. And there are many experts out there who will ignore these types of tips because they seem too simple. I happen to think things like this are important so I will dwell on things like this instead of the next breakthrough technology in pulse welding. Anyway, one of the methods and probably the easiest is to use a square. We won’t go into details about this for obvious reasons. The other two methods involve a little deeper thought but, not much.
Let’s say you are building a trailer frame. Let’s also say that it is 16′ long x 8′ wide. A framing square is not going to do you much good since it is too small to get very accurate readings. In this case you will want to grab your tape measure and measure from one outside corner to the opposite outside corner. If this measurement is exactly the same, then the frame is perfectly square. If it’s not the same then needless to say it is out of square. For instance, if one corner to corner measurement is 240″ and the other corner to corner measurement is 241″, your frame is 1/2″ out of square. The math says it’s a difference of 1″ but, it’s like we are working with two separate triangles so each one is out of square 1/2 of an inch, hence the term 1/2 inch out of square. Now you can work with the frame by pushing the two longest corners together until the are both measuring 240 1/2″ in a relaxed state.
Now let’s say you are working on an object that is not a rectangle but, instead is an “L” shape. For instance putting a headache rack on a flatbed truck. Now you can use a square but, to be more accurate you might want to use the 3-4-5 method. The math theory behind this method is if one leg of an angle is 3′ and the other leg is 4′ the hypotenuse must be 5′, the math doesn’t lie. So the application for the flatbed will go like this. If you measure up from the bed of the truck and put a mark on the headache rack at 3′. Then measure from the base of the headache rack and mark the flatbed at 4′. the exact measurement from mark to mark should be exactly 5′. If it’s not, you have some adjusting to do. The 3-4-5 method works with any numbers that are divisible to it’s corresponding number. For example 30′ and 40′ should be a 50′ hypotenuse. Another example is 18″ and 24″ should be a 30″ hypotenuse, you get the idea. That’s really all there is to it, quite simple once you get the hang of it. Don’t be intimidated by all the big words I just used, I had to look up the meaning of most of them. (just kidding, It’s safe to use these methods)