Gutou Sun (箍头榫): How Beams Clasp the Corner Columns of Chinese Buildings
Gutou sun · Clasping tenon
At the corners of a Chinese building, the tie beams don’t stop at the column. They run straight past it and end in a carved head.
That head is doing a job. The gutou sun, the clasping-head tenon, locks the beam to the column so it can’t be pulled away.
- Chinese
- 箍头榫 · gūtóu sǔn
- Joins
- Tie beam to end or corner column
- Found in
- End bays and corners of timber buildings, pavilions
- Proportions
- Tenon 8/10 of beam height, 1/4–3/10 of column diameter wide
- Head
- 霸王拳 (large style) or 三岔头 (small style)
How it works
Slot in the column head
A slot is cut across the top of the column. On a corner column where beams arrive from two sides, slots are cut both ways.
Narrow tenon, wide head
The beam end is cut to a tenon about 8/10 of the beam’s height and no wider than 1/4–3/10 of the column diameter. It drops into the slot from above, and the beam continues past the column as a head about 8/10 of the beam’s size.
How far it runs past
Measured from the column centre, the head runs one column diameter with a 霸王拳 (“overlord’s fist”) end, used on large-style buildings with bracket sets, or 1.25 diameters with a 三岔头 end on small-style ones. Where two beams cross at a corner they are halved over each other, the side beam over the front.
How it's made
Step 1Slot the column
Cut a slot across the column head.
Step 2Cut the tenon
Narrow the beam end to a tenon that fits the slot.
Step 3Leave the head
Let the beam run past the column as a head.
Step 4Drop it in
Drop the beam into the slot from above.
Step 5Clasp
The head clasps the column.
Step 6Locked
The beam can’t be pulled away.
Variations
One-sided
On an end column, the slot runs one way.
Crossing at a corner
Two beams cross in a cross-slot, halved over each other.
Head forms
霸王拳 on large-style buildings, 三岔头 on small-style ones.
Related joints
Column-Head Tenon (馒头榫)
A short square tenon on the column head fits a socket under the beam, so the beam can’t slide off.
Big-In, Small-Out Tenon (大进小出榫)
Part blind, part through: a big tenon enters, a small one shows. It lets two stretchers share a leg without weakening it.
Column-Foot Tenon (管脚榫)
A short round tenon at the column foot drops into a socket in the stone base, so the column can’t shift.
Questions
What is a gutou tenon?
The joint where a tie beam drops into a slot in an end or corner column and runs past it in a head that clasps the column.
How far does the head project?
One column diameter from the column centre for a 霸王拳 head, 1.25 for a 三岔头.
Why let the beam run past?
The head locks the beam to the column.