modeling - Cutting a mesh in half - Blender Stack Exchange
Cutting mesh in Blender (sculpt mode) - Blender Tests - Blender Artists Community
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Blender Knife Tool
Cutting out complex shapes can be time-consuming, and on a curved surface it can be almost impossible to get right. Luckily, there's a tool called knife... | By Blender Secrets | Facebook
How to cut out a shape in your object in Blender? - Artisticrender.com