This filter is found in Filters → Render → Pattern → Grid.

It renders a Cartesian grid in the active layer, on top of the existing contents. The width, spacing, offsets, and colors of the grid lines can all be set by the user. By default, the lines are with the Gimp's foreground color. (Note: this plugin was used to create demonstration images for many of the other plugins.)

	Tip
	If you set the grid line widths to 0, then only the intersections will be drawn, as plus-marks.

There are separate options for controlling the horizontal grid lines, vertical grid lines, and intersections. By default, the horizontal and vertical settings are locked together, so that all changes are applied symmetrically. If you want to change just one of them, click on the "chain" symbol below it to unlock them. The results of changing the "intersection" parameters are rather complex.

Besides, for some options, you can select the unit of measurement thanks to a drop-down list.