Kento is Japanese for Registration Marks in Japanese Printmaking or Moku Hanga.
'The genius of the kento system of registration lies in its very simplicity. The position of the kento is fixed in relation to the image on the original drawing/keyblock and faithfully transferred to each block. The principle maintains exactly the size of the margin around the printed area on each block thus guaranteeing accurate registration. ' (Rebecca Salter)
**Taken from the book, Japanese Woodblock Printing by Rebecca Salter, 2001. I highly recommend this book if you're looking for a good reference for woodblock printmaking! You can buy it at McClain's.