Every image opened in GIMP 2.8 displays a ruler around it for at-a-glance measurements during image composition. While usually the default setting of pixels works fine, in some cases using a different unit of measure is preferable – like using inches while designing a standard 3.5-by-5-inch postcard. The ruler tool, located at the bottom of the current image, is the only means to swap the units displayed on the ruler.
