Chinese JoineryChinese Joinery
中文
Luban lock
十二柱鲁班锁
shí'èr zhù lǔbān suǒ

Twelve-Piece Luban Lock (Altekruse): 3D & STL

Altekruse · 4-4-4 · 十二根

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Twelve identical notched sticks, often described as four per axis (4-4-4). In the literature this family is the Altekruse puzzle (US Patent 430,502, 1890; Coffin’s Puzzling World ch.6).

Unlike the six-piece Chinese cross, every stick is the same shape. The first move is a mutual opposite half-slide of two halves — not a single key.

Pieces
12 identical sticks
Literature
Altekruse · Coffin SOS
First move
Mutual opposite half-slide
Atlas name
十二柱 (folk count)

Assembled twelve-piece: twelve identical SOS sticks, four per axis (4-4-4), locking each other.

Drag to rotate. Coffin SOS / A-B-A (end notches same way, middle opposite); US Patent 430,502; first move is a mutual opposite half-slide. Teaching voxel box-soup mesh, not a manifold boolean.

Drag to orbit; scrub the slider for the half-slide.

How it works

How it bites

Each stick carries three half-depth notches. Oriented copies fill four sticks per axis without overlapping voxels. Pulling one half opposite the other opens the knot.

Market “十二柱” toys may cut different notches; this page follows the Coffin SOS form.

Free STL downloads

All twelve sticks are identical — prefer printing the single SOS stick twelve times. Teaching voxel box-soup; suggest 8–10 mm/u. Licence CC BY 4.0. See the CNC and 3D-printing notes.

Open preview gallery →

Questions

How is twelve-piece different from six-piece?

All twelve sticks are identical; the first move is a mutual half-slide, not pulling a single unnotched key.

Can I print it?

Yes. Prefer printing the single SOS stick twelve times. STL downloads and CNC notes are on this page.

Further reading
  1. Stewart Coffin / John Rausch, Puzzling World ch.6 — Altekruse
  2. William Altekruse, US Patent 430,502 (1890)