Shells

Shells are collections of connected faces in OCCT, sitting between individual faces and closed solids in the shape hierarchy. They matter when a surface has to be treated as one continuous skin: sewing separately built faces into a watertight boundary before converting to a solid, or working with an open surface that is deliberately not closed. These pages cover creating shells by sewing faces together, checking whether a shell is closed, and converting a closed shell into a solid. This is also where you go when a solid operation fails because its boundary has gaps.