Men Sun (闷榫): The Fully Hidden Dovetail
Men sun · Blind mitred dovetail · 暗榫
Some Chinese low tables are made of just three thick boards: a top and two board legs. At each corner you see one clean diagonal line and nothing else.
Inside is a men sun, literally a “stuffy” or closed-in tenon: dovetails completely hidden behind a mitre.
- Chinese
- 闷榫 · mèn sǔn
- Also called
- 暗榫; modern woodworkers say 全隐燕尾榫
- Joins
- Thick boards at a corner; thin drawer sides
- Found in
- Board-leg kang and side tables, fine drawers, small boxes
- Signature parts
- Mitred outer skin · hidden dovetails
How it works
Three thick boards
Wang Shixiang describes kang and side tables made of three boards up to 4–5 cm thick. Where the top meets the board legs, every example he saw used a men sun: after closing, only one seam shows and all the joinery is hidden.
Dovetails inside
The corner is mitred on the outside. Behind the mitre, dovetails on one board fit sockets in the other, so the boards can’t pull apart.
Drawers too
The same idea, made finer, joins very thin drawer sides in small pieces such as document boxes and mirror stands. It is the most refined of the board-corner joints, above the open dovetail and the half-hidden one.
How it's made
Step 1Mitre the corner
The two thick boards meet at a mitre.
Step 2Cut hidden dovetails
Dovetails are cut inside the mitre, short of every outer face.
Step 3Cut the sockets
Matching sockets are cut inside the other board.
Step 4Slide together
The boards are slid together.
Step 5Skin covers all
The mitred outer skin hides every dovetail.
Step 6One seam
Closed up, only a single seam line shows.
Variations
Through dovetail
Both faces show the dovetails; Wang says only rough folk pieces used it on drawers.
Half-hidden dovetail
Shows on one face only.
Hooked mitre
A quicker look-alike for aprons that can work loose with age.
Can you CNC this?
Hard on a 3-axis machine as drawn
Hard: the dovetails are hidden inside a mitred corner, so their undercut faces are enclosed and cannot be reached by a 3-axis cutter. A practical CNC alternative is a plain mitre with a spline or loose tenon, which changes the joint.
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)
- Top member 上方构件 · men-sun-top-member.stl
- Leg with hidden tails 带暗燕尾的腿 · men-sun-leg.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
Dovetail Joint
yànwěi sǔnA tenon wider at the tip than at the root, so it can’t pull out: found in boxes, drawers, tables and temple beams.
Breadboard End
pāi mǒtóuA cross-grain strip mitred and tenoned onto the end of a thick board: no end grain shows, and the board resists splitting.
Mitred Frame Joint
géjiǎo sǔnThe 45° corner of every Chinese frame-and-panel top: a tenon through the end plus a little triangular tongue.
Questions
What is a men sun?
A corner joint for boards with dovetails completely hidden inside a mitre, so only a seam line shows.
Where is it used?
Thick-board kang and side tables, and the drawers of fine small furniture.
How is it different from a normal dovetail?
A normal dovetail shows on one or both faces; a men sun shows nothing but the mitre.