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The Joints Nobody Sees — lesson illustration Standard

MATERIALS & BUILDING

The Joints Nobody Sees

  • 12 spell
  • 4 known
  • 3 semi-open
  • 5 open
  • 3 math
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THE HIDDEN JOINERY OF HORYUJI

In Ikaruga, outside NARA, a five-story PAGODA has stood for roughly thirteen centuries. Part of the temple complex at Horyuji, it is among the oldest surviving wooden buildings in the world, and almost none of the carpentry holding it up is visible. The joints are buried inside the timbers, cut so that two pieces lock by shape alone. CARPENTERS trained to build and repair such halls are called MIYADAIKU, temple carpenters, taught hand to hand over decades rather than from books. Their finest work is sealed inside, where no visitor will ever look.

  1. SPELL
    MIYADAIKU
  2. SPELL
    CARPENTERS
  3. KNOWN
    What is the five-story tower at Horyuji, standing for some thirteen centuries, called?
    Answer: PAGODA
  4. KNOWN
    Ikaruga sits just outside which city?
    Answer: NARA
  5. OPEN
    The best work in that building is sealed inside where nobody will ever see it. What is something you would do well even if no one could check?

TWO FAMILIES OF JOINTS

Japanese carpenters sort their joints into two families. TSUGITE are splices, joining two timbers end to end so that a long beam can be made from shorter ones, or a rotten foot cut away and a sound piece let in. SHIGUCHI are the connections where members meet at an angle, post to beam or beam to beam. Neither family needs nails or glue. A MORTISE is chopped into one piece, a TENON cut on the other, a DOVETAIL flares so it cannot pull straight out, and a HARDWOOD WEDGE drives the assembly tight.

  1. SPELL
    TSUGITE
  2. SPELL
    SHIGUCHI
  3. SPELL
    HARDWOOD
  4. SEMI-OPEN
    Name two of the cut shapes that lock a joint together without nails or glue.
    Needs 2 of: MORTISE, TENON, DOVETAIL, WEDGE
  5. OPEN
    A rotten foot of a post can be cut away and a sound piece let in. What is something you own that you would want mended instead of replaced?
  6. MATH
    Suppose a carpenter splices a four-meter timber to a three-meter timber, and the overlap of the splice takes up one meter. How many meters long is the finished beam?
    Answer: 6

MARKING THE WOOD

The wood is usually HINOKI, a slow-growing Japanese CYPRESS prized because it is straight-grained, aromatic, and stubbornly resistant to rot. Nothing is cut until it is marked. The carpenter snaps guide lines with the SUMITSUBO, an ink pot holding a soaked line on a reel, and every cut afterward answers to those lines rather than to a fresh measurement. Only then do the cutting tools come out: a SAW that bites on the pull stroke, a CHISEL for clearing waste, an ADZE for roughing a face, and a PLANE, likewise drawn toward the body.

  1. SPELL
    SUMITSUBO
  2. SPELL
    HINOKI
  3. SPELL
    CYPRESS
  4. SEMI-OPEN
    The carpenter keeps four cutting tools for shaping the marked wood. Name two of those tools.
    Needs 2 of: SAW, CHISEL, ADZE, PLANE
  5. OPEN
    The saw and the plane both cut while being pulled toward the body instead of pushed away. What do you think that pulling motion would feel like?

TAKING IT APART

Hidden work cuts both ways: a joint nobody sees is also a joint nobody can check. The tradition's answer is that buildings come apart. Every few generations a temple is dismantled down to its members, and the damage done by ROT, INSECTS, EARTHQUAKES, and WEATHER is read out of the timbers one piece at a time; decayed sections are spliced out and the frame goes back up. ISE JINGU goes further, rebuilding the shrine on a fixed twenty-year cycle called SHIKINEN sengu. The sixty-second rebuilding came in 2013, leaving a shrine both ancient and new.

  1. SPELL
    SHIKINEN
  2. SPELL
    JINGU
  3. KNOWN
    Which named Jingu, the shrine rebuilt on a fixed twenty-year cycle, sits at the far end of this tradition?
    Answer: ISE
  4. SEMI-OPEN
    Name two of the forces that damage a wooden building over time.
    Needs 2 of: ROT, INSECTS, EARTHQUAKES, WEATHER
  5. OPEN
    When a temple is taken apart down to its separate pieces, which piece would you most want examined first?
  6. MATH
    The shrine at Ise is rebuilt every twenty years. How many rebuildings happen over three hundred years?
    Answer: 15

WHAT YOU CANNOT SEE

You own a version of this problem already. Wood never stops moving: as it dries and as HUMIDITY swings, a board loses and regains width across the grain, a change called SHRINKAGE, and anything glued or screwed rigidly against that movement eventually splits or works loose. A dovetail cut to slide, a tenon fitted to breathe, a wedge that can be knocked back out — these let a thing be taken apart and put back together instead of thrown away. The next time a drawer still runs sweetly after GENERATIONS of use, look at what you cannot see.

  1. SPELL
    GENERATIONS
  2. SPELL
    HUMIDITY
  3. KNOWN
    What is the term for the way a board loses and regains width across the grain as the air dries and dampens?
    Answer: SHRINKAGE
  4. OPEN
    What object would you most want to take apart to see how it was put together?
  5. MATH
    Suppose a drawer front measures 200 millimeters across the grain and dry air shrinks it by 3 percent of that width. How many millimeters narrower does it become?
    Answer: 6

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