Calligraphers and artists often put two seals under their signature—usually one with red characters and one with white characters. The purpose of a “T” shaped seal ruler is to help position these two closely spaced seals on your artwork without the extra bother of moving and repositioning an “L” shaped seal ruler. If you aren’t careful with an “L” shaped ruler (or stamping the seals freehand) you might smudge the first seal while applying the second. The drawback to the “T” shaped seal ruler is is that you’re unable to adjust the spacing between the two seals, which is determined by the width of the ruler. The “T” ruler is especially useful when you have two seals which you use frequently where this spacing is appropriate. It’s fairly easy to make your own seal ruler with different spacing for different size seals.