Just a simple square grid that's easy to place anywhere as a material.
Need thicker lines? Add the "Border Effect" in layer property and adjust size as needed.
I needed a grid that was a placeable, tileable material that I could adjust after the fact. Well, here it is.
If you want to make the lines thicker, go to the "Layer Properties" window and add the "Border Effect" and make the line black. Then, adjust thickness until you have the size lines you want.
I would not recommend using this for the final image since this is more for helping out with aligning things or in the sketch phase, but it's your art, do what works for you! I just hope this grid help.