Many graphics editor apps like Add Text has some kind of in-build grid to help the user with positioning of graphical elements. But the in-built grid is often not enough for more complex work. Then, a custom grid is needed. You can see an example of such situation on the image that follows.
Another kind of grid you may find useful also as a help for image crop with Tasker. Placin a 10×10 or 20×20 grid over the image makes it much easier to determine the exact percents to be cropped from each side without many tries. See an example below.
Click the image for full size.
As usually, you can download a ZIP file with the basic grids used in this post from my site:)