Jiatou Sun (夹头榫): The Bridle Joint of Ming Tables

Jiatou sun · Clamping-head joint

The long, quiet tables of Ming China, painting tables and altar tables, stand on legs set in from the ends. Where each leg meets the top, it rises past a long apron and a pair of shaped spandrel heads.

Inside that junction is the jiatou sun, the elongated bridle joint. The leg is slotted at the top and literally clamps the apron, so the whole underframe becomes one rigid ring.

Chinese: 夹头榫 · jiātóu sǔn
Joins: Leg, apron, spandrel heads and top
Found in: Recessed-leg tables: painting, altar and side tables
Signature parts: Slotted leg top · apron · spandrel heads (牙头)
Look: The leg stands proud of the apron

Drag to rotate. Slide to take the joint apart, or press Assemble to watch it go together.

How it works

Borrowed from buildings

Wang Shixiang traced the joint to the Northern Song, when furniture makers borrowed from timber-frame buildings, where a column top is slotted to clamp a bracket. On tables the clamped pieces became one long apron, and spandrel heads were added beneath.

The slot

The top of the leg is sawn open. In the standard form the slot is long enough to clamp both the apron and the spandrel heads. The leg then tenons into the underside of the top.

Why it works

The apron gives the leg a much bigger grip on the top, so the angle between leg and top can’t easily change, and the weight of the top is spread evenly to all four legs.

How it's made

Step 1
Slot the leg
Saw an open slot down the top of the leg, deep enough for the apron and the spandrel heads.
Step 2
Tenon the leg top
Leave tenons on the leg top to go into the table top.
Step 3
Shape the spandrel heads
Cut the spandrel heads to fit in the slot below the apron.
Step 4
Drop in apron and spandrels
Lower the spandrel heads and the apron into the slot.
Step 5
Set the top on
Fit the top over the leg tenons.
Step 6
Check the look
The leg stands proud of the apron and spandrels on the outside.

Variations

Slot clamps the apron only

The spandrel heads are thin upright pieces set into grooves on either side of the leg.

Grooved, not slotted

The leg is only grooved and the apron is in sections. Wang called this showy but weak; it spread after the mid-Qing.

Can you CNC this?

Possible, with design or setup changes

The slot in the leg top and the tenon into the top are straightforward if the leg can be clamped upright or cut from the sides. The spandrel’s outline is a 2D profile; any carving on it is a separate 3D job.

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)

Leg 腿足 · jiatou-sun-leg.stl
Spandrel 牙头 · jiatou-sun-spandrel.stl
Apron 牙条 · jiatou-sun-apron.stl
Top 桌面 · jiatou-sun-top.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).