How To Make Square Cuts In Dimensional Lumber

Its important to get square cuts in wood when building certain projects. Square cuts allow you to create stronger joints and allows you to have your pieces fit together properly so that planter bench youre trying to build is straight and doesnt wobble.
There are a number of different ways that you can make square cuts in dimensional lumber such as 1x6s, 2x4, 2x6s, etc., which vary in price. Most will also allow you to make accurate angled cuts such as 45 degree cuts.
As with any tools, make sure to read, understand and follow all instructions that come with the tools.

Good

Speed Square and Circular Saw

The cheapest and quickest way to make square cuts in dimensional lumber if you already have a circular saw is to use a Swanson Speed SquareIts important to follow the guide carefully and to have a good circular saw that will sit flat on its base and can be adjusted to a true 90 degrees.  I have a cheap circular saw that I bought for around $40 that was used for some demolition. Im not sure if it ever sat flat or was able to get the blade square but its difficult to get it to now.
If youre using this method do a test cut to make sure the cuts are coming out square. You can use the speed square to measure the angle of the cut.

Better

Miter Box

A miter box is a plastic box that has slits cut at precise angles that guide the saw to allow you to make fairly accurate angled cuts in molding or dimensional lumber. Years ago you could find affordable wooden miter boxes but these days all I see are the plastic ones like the Stanley 20-600 Clamping Miter Box

The Stanley 20-800 Contractor Grade Clamping Mitre BoxIf you like the idea of a manual miter saw that is safer, cleaner and quieter than a power miter saw but want something a little better you can have a look at the Nobex Proman Miter Saw

A power miter saw like the Hitachi C10FCE2 10-Inch Compound Miter Saw