Several years ago I became aware of the work of Kintaro Yazawa, who, according to a 1986 article in FWW (issue 61), had taught furniture maker Alan Peters about the twisted dovetail joint, or nejiri ari gata. The name of the joint in Japanese, I might add, terms what we call a 'dovetail' in the west an 'ant-shape'. The 'twisted ant-form' joint then.
A while later, Yazawa had re-established himself in Japan as a specialist in joinery and makes small presentation boxes and pieces of furniture incorporating technically difficult or 'impossible' looking joints. A few years ago there was a second article in FWW by Yazawa illustrating a couple of his methods and this seems to be the point where a bunch more people, in North America at least, became aware of the craftsman and his marvelous work.
I've had pictures of a couple of his pieces on my computer, in a special folder, for several years now. Like Yazawa, I love joinery and also share a liking for puzzle joints of all kinds.
There are various basic forms of 'puzzle joints'. Some are made to be puzzles which just so happen to be wooden, though they could be in other materials. The other is a form of wooden joint which is assembled by apparently impossible means.
Of the former type of puzzle, there are what are known as karakuri. These have long been known in the west, as examples were brought over from Japan since the late part of the 19th century. Here's a very simple form of karakuri puzzle box:
There are boxes like this with hundreds of moves required to get them open - one that I've come across requires 1536 moves!
Another popular type of puzzle involves interlocking sticks - these are termed kumiki in Japanese, and ’burr puzzles’ in English-speaking countries. Here's a typical example sitting on my desk:
In the above types of puzzles, while the mechanism by which the puzzle goes together may be mysterious at first - or for a long while, as the case may be - with puzzle joints in woodworking, the joints cannot often be readily separated, either because they are incorporated in a larger structure, or because they are glued together, or because the assembly of the joint is such that it will not permit dis-assembly. There are also a small number of joints in which dis-assembly is possible, but difficult, in which case they are not significantly different than the wooden puzzles above.
The key difference, it appears to me, is that puzzles are usually readily recognized as puzzles - like the burr above, or are quickly found to be puzzles, as one might readily discover when trying to open one of those puzzle boxes. You know it's a box, and there might be something inside, but how does it open?
With wooden joints which are puzzles, I would say that unless one is a woodworker who does joinery in solid wood (a minority of woodworkers) and knew how such joinery goes together, one likely wouldn't notice anything odd about a puzzle joint. It's the ultimate in stealth I suppose, however the message, as such, is more or less lost on most who see the construction.
A great case in point would be the Ōtemon, a gate at Ōsaka Castle:
Here's a view from the inside looking out:
Both gateposts have unusual 'rot joints' - these are spliced in replacements for the bottom few feet of a posts that have rotted out.
A closer look at the joint on the post seen to the left in the above picture:
Here's one side:
And the other:
Ignoring the other stuff going on at the connection, such as the missing plug part way into the front dovetail (to cover a metal bolt anchoring the joint to a lateral tie to the rear), and the end of a diagonal brace sticking out above the joint, we see a splice in which two opposing faces are dovetails, and two opposing faces are like a sword tip, or mountain peak if you prefer. If your response is 'so what?' perhaps take a moment to consider how such a connection might assemble in wood....
I would guess several million people walk past that gatepost every year, but only a tiny fraction notice anything unusual about that joint. For carpentry geeks of all stripes however, this is a delight! The Ōtemon-splice is famous in Japanese carpentry, and also goes by the name of basara-tsugi. Lots of Japanese carpenters know about it and have incorporated it into their work. Here's an example of a freshly-installed one:
I just finished cutting one for a client, as on of several joinery models I am making. I might add that there are many other forms of rot-splice joints, and several of them incorporate a 'how'd they do that?' aspect. I'll save that for another blog entry some day. I do detail the mechanism of the basara joint in the Volume III essay of the TAJCD series, BTW.
Getting back to Yazawa, some of his joints are mysterious from the aspect of being incredibly hard to execute, like this one:
The assembled joint:
Other joints he makes however feature a means of assembly which is, to put it mildly, hard to determine. Case in point is this box, which employs what Yazawa calls a 'key hall' joint on the Japanese portion of his site (I'm sure he means 'key-hole' joint):
Another view of the corner of the above box:
A view from the inside reveals nothing special, which is itself special in this case:
That joint is but a warm up of sorts, however, for this one, a joint that Yazawa terms the 'transcendence joint':
A look at an 'impossible' corner:
Please be clear that all these joints are done in solid wood without recourse to veneering or gluing pieces together. I've read some online discussions where people put forth theories involving such ideas, and they are false.
I spent some time working on the joint for the 'key-hole' joint above, thinking it was an easier puzzle to crack than the transcendence joint, and thinking they may have some commonalities in their mechanism.
I emailed Yazawa several years back asking him for a hint, and he replied that the secrets were going with him to the grave. Okay, well, then, I see how it's going to be....
So, I left the puzzle on the digital 'shelf' of my computer, occasionally bringing it down to look at it again. Recently I got a bit more fired up about it and managed to solve the key-hole joint, working at it with a 3D drawing. I figured out an initial solution involving pivoting moves. I shared my drawings with Yazawa, and he gave me all sorts of encouragement (indicating that I had it wrong, but keep trying). No hints of course, or even a nod that I might be on the right track, which I don't mind. I don't want the solution simply handed to me on a platter. When I found a second solution to the problem, and the only solution (probably) which can work for a 4 sided box, I sent him those drawings. He hasn't replied and it has been a week, so not quite sure what to make of that. Maybe he's annoyed. I won't presume to reveal the secret of that joint here - if it intrigues you, put some time in and try and solve it yourself.
The transcendence joint is next in my sights, and it is proving to be quite tough to solve so far. I'll keep plugging away at it however and hopefully will also transcend the problem at some point myself.
I think that the study of karakuri puzzle mechanisms of all kinds will be very helpful for solving such mysterious joints, and for creating new ones.