Guanjiao Sun (管脚榫): The Column-Foot Tenon
Guanjiao sun · Column-foot tenon
Chinese timber columns usually stand on a stone base rather than in the ground. A small tenon at the foot keeps each one in place.
It is the guanjiao sun, literally the tenon that “manages the foot”.
- Chinese
- 管脚榫 · guǎnjiǎo sǔn
- Joins
- Column foot to stone base
- Found in
- Timber-frame buildings
- Size
- About a third of the column diameter
How it works
A short round tenon
The foot of the column is cut to a short round tenon, about a third of the column diameter.
Into the base stone
It drops into a socket (海眼) cut in the top of the stone base (柱顶石). The column’s weight keeps it down and the tenon stops the foot sliding.
Through-base version
Where columns need extra anchoring, a much longer square tenon (套顶榫) passes through the base stone into the foundation below.
How it's made
Step 1Cut the tenon
Cut a short round tenon on the column foot.
Step 2Size
About a third of the column diameter.
Step 3Socket the stone
Cut a socket in the base stone.
Step 4Set the column
Lower the column onto the stone.
Step 5Located
The tenon stops the foot shifting.
Step 6Hidden
Once in place it can’t be seen.
Variations
Through-base tenon (套顶榫)
A long square tenon through the base stone into the foundation, for columns that need more anchoring.
Can you CNC this?
Possible, with design or setup changes
The socket is in the stone base, so it is not a wood-routing job. The round tenon on the column foot is easier on a lathe; on a 3-axis machine the column may need to stand upright.
General note: a round cutter cannot leave a sharp inside corner, so every recess keeps the tool radius. Round the mating edges or add dogbone reliefs. Sloping faces, undercuts and curves may need special bits, extra setups or more axes.
Free STL downloads (one file per part)
- Base stone 柱础石 · guanjiao-sun-base-stone.stl
- Column 柱 · guanjiao-sun-column.stl
Proportions are illustrative, not measured dimensions. The files are unitless: scale them to suit and check fits and allowances before cutting. Each file is a closed (watertight) solid with its mortises and slots already cut, exported in its assembled position, ready to import into CAM or modelling software. Licence: CC BY 4.0 (credit: Chinese Joinery).
Related joints
Questions
What is a guanjiao tenon?
A short tenon at a column foot fitting a socket in the stone base.
How big is it?
About a third of the column diameter.
Is the column buried?
No, it stands on the stone; the tenon only keeps it from sliding.