# Jigoku hozo (hidden wedged tenon)

> How does a jigoku hozo joint work?

- Category: Joinery › Japanese joinery
- Kind: Hardware
- Basis: Xem Studio design — geometry computed in the generator from traditional proportions
- Page: https://xemstudio.com/objects/jigoku-hozo-hidden-wedged-tenon/ · JSON: https://xemstudio.com/api/geometry?object=jigoku-hozo-hidden-wedged-tenon · Plain text: https://xemstudio.com/objects/jigoku-hozo-hidden-wedged-tenon/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 80.0 | 80.0 | 20.0 |

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Woodworking joint drawn for 3D printing: the parts lock together by shape, so a print can be joined without glue or screws. Drawn at true size with the parts line to line (zero gap) in their assembled position — add your printer's fit allowance to the mating faces (your AI or slicer can do this).
- Jigoku hozo — "hell tenon": the wedge waits at the bottom of a blind mortise, and driving the tenon in spreads it into the flared mortise, so the joint can never be taken apart. Drawn in the assembled (spread) state.

## Sizes

| dimension | value |
|---|---|
| stock | 20 × 20 mm square |
| parts | mortised member, tenon member, wedge |
| mortise | 10 mm at the face → 14 mm at the bottom, 15 mm deep |
| wedge | 4 mm head, 12 mm long |
| assembles | wedge set in the tenon's kerf; driving the tenon home spreads it — it cannot come out |
| holds | pull-out, permanently |

## Where the files are

- Xem Studio: [Joinery design (geometry computed in the generator from traditional proportions)](https://xemstudio.com/) — web — Xem Studio design

## Free STEP/STL (4 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/index.json · license: https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/LICENSE.md

- jigoku-hozo-hidden-wedged-tenon-mortised-member: [STEP](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-mortised-member.step) · [STL](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-mortised-member.stl) — Blind mortise flared 2 mm per side toward its bottom
- jigoku-hozo-hidden-wedged-tenon-tenon-member: [STEP](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-tenon-member.step) · [STL](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-tenon-member.stl) — Tenon split at its end, shown spread (assembled state)
- jigoku-hozo-hidden-wedged-tenon-wedge: [STEP](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-wedge.step) · [STL](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-wedge.stl) — Wedge sitting at the bottom of the mortise
- jigoku-hozo-hidden-wedged-tenon-assembled: [STEP](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-assembled.step) · [STL](https://xemstudio.com/files/hardware/jigoku-hozo-hidden-wedged-tenon/jigoku-hozo-hidden-wedged-tenon-assembled.stl) — All parts in their assembled position (each part its own solid)

## Questions

**Why is it called hell tenon?**

Once driven home it can never come out.

## Fits with

- [Wedged through tenon joint](https://xemstudio.com/objects/wedged-through-tenon-joint/)
- [Blind mortise and tenon joint](https://xemstudio.com/objects/blind-mortise-and-tenon-joint/)