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Luban lock
六柱鲁班锁
liù zhù lǔbān suǒ

How to Solve a Luban Lock: Six-Piece Burr Puzzle Solution

Six-piece burr · Chinese cross · 小孔明锁

By · Updated

The classic Luban lock — also called the Chinese cross — is six square sticks of equal length. Once the last piece seats, nothing leaves until the key moves first.

This page walks one working set — von Känel pieces {1, 256, 824, 928, 975, 1024} — with an interactive take-apart, six assembly diagrams, and free STL files.

Pieces
6 (set {1, 256, 824, 928, 975, 1024})
Key
Piece 1 — unnotched stick
Also called
Chinese cross · six-piece burr
Kind
Interlocking puzzle (not a furniture joint)

Assembled: six notched sticks, two along each axis, locking each other.

Drag to rotate. Piece numbers follow J. von Känel’s six-piece burr numbering; this set is {1, 256, 824, 928, 975, 1024}.

Drag to orbit; scrub the slider to take the lock apart.

How it works

How the cross locks

Six sticks occupy three axis directions. Along each tunnel sit two sticks, nose to nose; their notches leave room for the other tunnels. When every stick is seated, each notch wall is blocked by a neighbour — until you remove the key.

This piece set

Piece 1 is the solid key. The numbered sticks are notch-pattern codes as listed on Rob’s Puzzle Page. The interactive model and the six diagrams follow the same path.

How to assemble (six steps)

  1. Seat piece 256
    Step 1

    Seat piece 256

    Stand the first notched stick. Everything else builds around it.

  2. Slide piece 928 home
    Step 2

    Slide piece 928 home

    Slide it along its length into the open tunnel.

  3. Push piece 824 home
    Step 3

    Push piece 824 home

    Push from the side until the notches seat.

  4. Lower piece 975 home
    Step 4

    Lower piece 975 home

    Drop it straight down into the crossing.

  5. Push piece 1024 home
    Step 5

    Push piece 1024 home

    Push from the side; five sticks now leave the key channel.

  6. Slide the key (piece 1) home
    Step 6

    Slide the key (piece 1) home

    Last: the unnotched stick. The knot locks.

    Tip To take it apart, reverse the list: key first.

Free STL downloads

Before cutting or printing, read the CNC and 3D-printing notes. Parts are exported in assembled coordinates, unitless — scale them and test the fit. Licence CC BY 4.0. See the CNC and 3D-printing notes.

Questions

How do you solve a six-piece Luban lock?

For this set, assemble 256 → 928 → 824 → 975 → 1024 → key (piece 1). Disassemble in reverse: key out first.

What is the key piece?

In many solid six-piece burrs the key is the unnotched stick (piece 1 here). It slides out first and frees the notched sticks.

Can I 3D-print this set?

Yes. Free STL files for each of the six pieces are on this page (CC BY 4.0). Scale them to suit and test the fit.

Is a Luban lock a furniture joint?

No. It is an interlocking puzzle that uses mutual locking, not a structural joint of furniture or buildings.

Further reading
  1. Burr puzzle, Wikipedia
  2. Rob Stegmann, Interlocking puzzles — “Some Common Six-Piece Burr Designs”
  3. Piece set {1, 256, 824, 928, 975, 1024}: J. von Känel numbering; assembly checked by tools/burr_solve.py