Blender Market: https://blendermarket.com/products/50-modeling-issues-from-hell
Gumroad: https://gumroad.com/l/50-modeling-issues-from-hell
Why my boolean operations produce non-manifold meshes with holes in Blender? There are many possible reasons, here are 10+ most common ones.

00:00 - Start
00:35 - Intro
01:32 - Non-manifold geometry
02:28 - 3D-Print Toolbox add-on for Blender
04:11 - Interior face
04:56 - Ripped edges
05:27 - Duplicate faces
06:00 - Duplicate faces (boolean objects)
06:43 - Missing faces (boolean objects)
07:27 - Flipped normals (boolean objects)
09:12 - Mirror modifier
10:30 - Co-planar polygons
11:19 - Flat (planar) boolean mesh
11:49 - Overlap threshold
12:21 - Outro

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50 Modeling Issues from Hell is the ultimate collection of 3d modeling tips for Blender.

Creative Shrimp: https://www.creativeshrimp.com/

Gleb Alexandrov: https://twitter.com/gleb_alexandrov
Aidy Burrows: https://twitter.com/AidyBurrows3D