When you apply a seal to your artwork, especially an important one, you want to be sure to get a good seal impression. Occasionally after you press your seal into the paper you get, instead, a very light impression (when the ink is dried out or the paper isn’t very absorbent). Without the use of a seal ruler it’s almost impossible (and not recommended to try) to re-stamp the seal in exactly the same spot. By aligning the inside corner of a seal ruler with where you want to place your seal you can, if you don’t move the ruler, re-ink and stamp it more than once.
Though usually translated into English as a seal ruler (印規 yingui) this tool has nothing to do with taking measurements. Seal rulers are usually in an “L” or “T” shape or as a flat disc with one quarter cut out. They can me made of just about any material; older ones are usually of wood or metal while modern ones are commonly made of plastic. And they may be plain or decorated. For aesthetic reasons traditional materials are often preferred but, in the case of this tool, modern clear plastic may be a better choice as you can see through the ruler and so more accurately position the seal where you want it on the page.
On the left is a homemade plastic ruler; on the right is a more traditional wooden ruler. As you can see, the clear plastic makes it easier to position the seals, especially when you use one above the other as seen here.
First, decide where you want to have the seal on your artwork. Then stamp the inked seal on a piece of scrap paper, the same kind as the paper or silk used for the art. If it looks like it may need to be re-stamped in order to get a clear impression, use the seal ruler as follows:
1) Place the un-inked stone in position and put the seal ruler next to it.
2) Being careful not to move the ruler, apply ink to the seal and stamp it on the paper. If the impression is clear, then you’re finished.
3) If it needs to be re-stamped, apply more ink to the seal and, being careful that the ruler hasn’t moved, press it again as many times as seems needed.
If you’re using two seals, one above the other and you want them aligned perfectly, first stamp one seal as above, then stamp the second seal.
In the art supply shops today most seal rulers are made from plastic. One shown below is a durable, commercially-made clear acrylic ruler. The round one, although looking brown, is actually clear plastic but still with the backing paper (to keep it in the store from getting scratched) with price tag. The blue one is a cheap, small, plastic ruler still in the package.
These are a couple of metal seals. And, as you can see, the round ruler is a complete circle with a removable section which could also serve as a decorative paperweight. [images taken from the internet]
Here are a couple of wooden seals. Both seem obviously expensive, with custom-made boxes. I’ve never seen anything like these for sale in any of the art supply stores I’ve been to, or sold anywhere online. [the images borrowed from the internet]
Seal rulers can be simply made from a curved section of bamboo—especially in Japan where natural materials are appreciated. Although aesthetically pleasing it may not be very practical since the raised middle of the curved section of bamboo is not in direct contact with the surface of the artwork. This means more chance of the seal shifting position the second time it’s stamped, defeating the purpose of the ruler. And just be sure, if you decide to make one, to sand the bottom edges so there are no splinters to scratch the surface of the artwork. [image borrowed from the internet]
Here’s two designs found on the internet with notches cut out of the inner corners; probably more decorative rather than functional.
Here’s a plan I found online for making your own seal ruler. They are easy to make and can be created from practically any material, though it should be smooth on the bottom so as not to scratch or tear the artwork.
And finally are some examples of what look like antique rulers [and once again with images found on the internet].
