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3-4-5 Triangle Method For Finding Square

Today i'm answering a subscriber's question by showing how to use the 3 4 5 triangle method for finding square this method is generally used when a square such as a framing square is just too small to get an accurate measurement of squareness for example this method can be used when framing walls decks porches it can be used for laying out flooring as well as large woodworking projects it has many uses and it's fantastic for establishing a 90 degree angle when you don't have one so what exactly is the three four five method well it's actually just a ratio between whole numbers and the smallest ratio that creates a right triangle happens to be three four and five this triple number or ratio has a name and it's called pythagorean triples what might be the coolest thing about these triples is that it's just a ratio and that means that as long as you keep the ratio there's an infinite amount of possibilities for example if i multiply each side by 2 i get 6 8 and 10 which is the same ratio and will produce a right triangle or i could multiply each side by 6 and get 18 24 and 30. the possibilities are endless so why is it so helpful to be able to change these numbers well it's because you can scale these triples up for large projects or you can scale them down for smaller projects for example if i'm building a small project i could use three four and five knowing that those measurements will actually take up most of the project's footprint or if i was building a large project where three four and five would only cover a small portion of the project i could use 18 24 and 30. what's also nice about these numbers is you can make them any unit of measurement you want for example 3 4 and 5 could be inches feet meters or any unit of measurement that works for you let's take a look now at two different ways to use this method the first way to use it is for squaring projects like for frames built-ins cabinets really any woodworking or carpentry related project for example here today i have a large wooden frame that needs check for square because of its size i'm going to use three feet four feet and five feet because it covers most of the size of the project and again that's a good thing because that means the accuracy will be greater the first measure will be taken from this corner on the outer edge over to the left three feet and let's make a mark the next measurement will be taken from that same corner now up the long side of the frame up to four feet and we'll make another mark the last measurement is taken between those two points which if our frame is square that measurement will be exactly five feet but in this case as you can see it's short by about a quarter inch or six millimeters therefore in order to square this frame up the frame would have to move at this end to the right until we've reached our measurement of five feet and as you can imagine if projects are large enough you will need a partner to hold the other end of the tape again this method can be used for large projects as well like home construction floor layout walls decks porches just to name a few i do have to mention at this point that there is another way to check this frame for square and that's to use diagonals this is where you measure from one set of corners diagonally and then from the opposite set of corners diagonally if these numbers match then you know the project is square we've actually already done a video detailing exactly how to do this and i'll leave a link in the notes section below so you can watch it after this one now that this frame is square as a whole we can also be certain then that this side here is coming off of this side squarely meaning that this is an exact 90 degree angle and no matter if we extend this line all the way out this piece will remain 90 degrees to this line regardless of what side we measure it from now that we cover the first method let's talk about the second method which is laying out 90 degree lines to each other some of the most common places for this to be used would be in floor layout like tile all aspects of home construction from rough to finish and of course some woodworking projects to demonstrate this method we're going to be using a chalk line so let's pretend that the line on the bench represents the threshold of an opening say into another room or space now in order to get a square line that runs through that other room we'll need to use the three four five method and to do this is pretty simple because it's very similar to the first method we start by making a reference point on this line and then measure over from that point three feet and make another mark with that take the chalk line now and extend it out which would be into that hypothetical room or in our case up the bench from there measure from the starting point up the string four feet make sure that the string is pulled taut and make a mark and i've always found it very helpful just to use a sharpie now all i have to do is swing the string either to the left or to the right until your diagonal measurement reads five feet and then snap your line with that now you know that these two lines are 90 degrees to each other and you can use that new line to help with whatever layout you need for your next project well that's it for today's video i hope it's been helpful of course if you have any questions or need specific help and like to share some photos and videos reach out to me on instagram thank you so much for watching i'll see you in the next video

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