In Western printing, long ago I started using registration boards. I've made them mostly of foam-board so that they could be fed through the etching press (or hydraulic press). A registration board is simply a "movable kento" system of registration. Any two pieces of material glued together as a square corner, then another piece of material as a paper guide glued at some pre-determined margin. Not really a complicated device. There is some error introduced in that the block has to be placed exactly in the same place every time, but in my experience this is less prone to error than having to cut exact kentos in as many as a dozen or more blocks. Seems that every kento in every block could introduce some error into the registration process and I would rather spend a little time upfront into building a semi-permanent movable kento.
With a well-built registration board, the only but very important requirement is that the blocks have to be cut perfectly square, the paper has to be cut perfectly square and the placement needs attention, but no more attention than if placing paper on a standard cut kento.
I used cheap wood and simple staples to see if the board worked okay for printing but I was careful to use a square at every step to make the board corner and the kentos a true 90 degrees. Also, the "ruler" is just cheap wood I had around the studio; I used it because it is slightly lower in thickness than my blocks, allowing the baren a free "ride" over the printing area without fear of catching on the registration guides. After a few prints, I brushed the whole board and mat-board kentos with clear acrylic to make it easier to repel water and clean pigment and paste off (not that I'm messy or anything).
Once I was satisfied that this was a suitable movable kento for woodblock, I made myself a slightly fancier board. This time I used a nice board for the backing and brass corners and straight pieces for the "kento". I brushed it with polyurethane again to make cleaning easier and installed semi-permanent one-inch and two-inch margin kentos. Despite the polyurethane, matboard still sticks to the wood, so I can still temporarily "install" a shorter or longer margin. Also the screws can be removed and the kentos moved according to my next project demands. I screwed the brass pieces quite firmly so that there would be absolutely no gap between the board and the brass kento where the paper could slip in. The whole board sits on a sheet of slip-proof drawer liner, which I also use sometimes directly under the block.
And again, I emphasize, the corners must be perfectly square, as the blocks and paper.
Much prettier, easier to clean.
Perfect registration is now a breeze, no need for cutting kentos on every block and wasting all that time and wood. Baren glides over the board without problems, cleanup a mere wipe with a damp towel, can life get any better than this?