Select a Square With Mac Preview

Lately I've been taking screenshots of code and my terminal. They seem to look the best when they're square; that shape translates better to a variety of project management tools and social media platforms.

Mac Preview lets you select part of an image down to the pixel for cropping, and I have found selecting a perfect square very difficult. The solution? Select with SHIFT + click to force a square-shaped selection. ⌘ + K to crop.