# What does Blender's 3D Print Toolbox check on a mesh before slicing (Solid, Intersections, Degenerate, Distorted, Thickness, Edge Sharp, Overhang), and what does each flag mean?

- id: art_01M5P243VWMC43A2BEC5QNMFHM
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T15, T16 · tags: none
- updated: 2026-10-24T04:18:53.940Z
- url: https://veyrul.com/articles/art_01M5P243VWMC43A2BEC5QNMFHM

Problem. A generated mesh looks fine on screen but a slicer needs a closed (watertight) surface. Conditions. Mesh selected in Blender with the 3D Print Toolbox enabled (bundled add-on in 3.6; listed as a Blender extension later). Method. Open 3D Viewport > Sidebar > 3D-Print, run Check All or single checks; in Edit Mode, clicking a result selects the offending parts. Solid flags non-manifold edges (edges not shared by exactly 2 faces) and bad contiguous edges (a flipped face). Intersections, Degenerate (zero area/length), Distorted (non-flat quads/ngons that triangulate unexpectedly), Thickness (thin faces), Edge Sharp and Overhang are separate checks. Failure modes. Per the manual, some slicers tolerate intersections, so a flag is not always fatal; results are analysis only, not a repair. Limitations. English page read is the 3.6 manual (latest path 404 at fetch); no numeric thresholds were on the page text read; check defaults live in add-on settings not read here. Version and dat...

Problem. A generated mesh looks fine on screen but a slicer needs a closed (watertight) surface. Conditions. Mesh selected in Blender with the 3D Print Toolbox enabled (bundled add-on in 3.6; listed as a Blender extension later). Method. Open 3D Viewport > Sidebar > 3D-Print, run Check All or single checks; in Edit Mode, clicking a result selects the offending parts. Solid flags non-manifold edges (edges not shared by exactly 2 faces) and bad contiguous edges (a flipped face). Intersections, Degenerate (zero area/length), Distorted (non-flat quads/ngons that triangulate unexpectedly), Thickness (thin faces), Edge Sharp and Overhang are separate checks. Failure modes. Per the manual, some slicers tolerate intersections, so a flag is not always fatal; results are analysis only, not a repair. Limitations. English page read is the 3.6 manual (latest path 404 at fetch); no numeric thresholds were on the page text read; check defaults live in add-on settings not read here. Version and date. Blender 3.6 manual, updated 06/23/2025.

Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources.

Limitations: Manual describes checks qualitatively; thresholds, and whether the 4.x/5.x extension changed behaviour, were not verified. The Solid wording is the Blender manual's, which counts 3+ faces per edge as non-manifold only by implication ('exactly 2').

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://docs.blender.org/manual/en/3.6/addons/mesh/3d_print_toolbox.html",
      "note": "Checks > Solid; Checks > Degenerate; Checks > Thickness; Checks > Overhang; Checks > Intersections"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Problem. A generated mesh looks fine on screen but a slicer needs a closed (watertight) surface. Conditions. Mesh selected in Blender with the 3D Print Toolbox enabled (bundled add-on in 3.6; listed as a Blender extension later). Method. Open 3D Viewport > Sidebar > 3D-Print, run Check All or single checks; in Edit Mode, clicking a result selects the offending parts. Solid flags non-manifold edges (edges not shared by exactly 2 faces) and bad contiguous edges (a flipped face). Intersections, Degenerate (zero area/length), Distorted (non-flat quads/ngons that triangulate unexpectedly), Thickness (thin faces), Edge Sharp and Overhang are separate checks. Failure modes. Per the manual, some slicers tolerate intersections, so a flag is not always fatal; results are analysis only, not a repair. Limitations. English page read is the 3.6 manual (latest path 404 at fetch); no numeric thresholds were on the page text read; check defaults live in add-on settings not read here. Version and date. Blender 3.6 manual, updated 06/23/2025. · locator: Checks > Solid; Checks > Degenerate; Checks > Thickness; Checks > Overhang; Checks > Intersections · source: https://docs.blender.org/manual/en/3.6/addons/mesh/3d_print_toolbox.html

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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