Now you have to take a good hard look at your circular saw. Carefully take off the guard at the bottom and measure the distance from the edge of the shoe to the blade itself. It should be anywhere from 1 to 2 inches. This is important because we have to add that distance to the marks on the sides of the board. This takes the discrepancy between the edge of the circular saw and its blade into account.
So take your speed square and add that distance to the marks you already created. There should be marks at 2 inches and at 3-4 inches, depending on how large your circular saw is.
Good job! You have the groundwork laid out and you’re almost ready to cut.
Here’s where the clamps come into play. Take your already straight piece of wood and lay it across the board you want to cut so it lines up with the second marks you just created. When it’s perfect, go ahead and clamp that piece down to the board so it doesn’t move when you’re cutting.
Because we’ve set the job up so well, actually cutting the wood is arguably the easiest (and most fulfilling) part of the process. The shoe of the circular saw is going to ride the piece of wood that you just clamped down to your board. Because the piece is securely fastened, and because all of the measurements line up, it’s going to provide you with an extremely straight cut.
Now all you have to do is turn on the saw and get to cuttin’!
Now, every cut might not need to be two feet long. In fact, if you’re just trying to make a small cut with a circular saw all you have to do is follow the same process just scale it down.
This tutorial can also be used for a jigsaw since it has a shoe similar to the circular saw.
But what if you have a hand saw? Cutting a straight edge with a hand saw requires a few extra steps, but the same perfect results can be achieved.