Grid is a mod that allows you to add markers to indicate where to place your blocks. It’ll help keep your spacing accurate as well as where your next block should go in the pattern. The grids can be displayed in a variety of ways like squares of a set size and squares of exact chunk sizes.

You can also set grids to display in a specific size like a 1×50 set of lines.

And even circular grids can help you build rounded corners and full circles.

And the grids can be fixed at a certain height or follow your position whatever level you’re on.

This mod relies on a few hotkeys as well as a variety of /grid commands so reference the forum page for those options.