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Hollow a body with Shell

Remove one face and leave an editable wall and floor thickness.

About 5 minCadivari 0.3.0Watch and try

Useful first: Turn a sketch into a solid

Shell hollows a supported solid by removing one selected face and offsetting the remaining faces inward. On an edited Extrude body, the starting shape must be one convex solid made of planar faces. Create the cavity before adding pockets or rounded edges.
Shell hollows a supported solid by removing one selected face and offsetting the remaining faces inward. On an edited Extrude body, the starting shape must be one convex solid made of planar faces. Create the cavity before adding pockets or rounded edges.

Shell hollows a supported solid by removing one selected face and offsetting the remaining faces inward. On an edited Extrude body, the starting shape must be one convex solid made of planar faces. Create the cavity before adding pockets or rounded edges.

Try it in Cadivari

  1. Start from the solid block

    Open a separate copy of the 160 × 96 × 15 mm Push/Pull practice block before any Fillet or Shell. Keep its top-face edit, but use a block with no pockets, holes or curved faces.

  2. Choose the opening

    Hide the source sketch if needed. Click Shell in the 3D rail, then click the top planar face. That face will become the opening, so choose the face rather than its edge.

  3. Preview the thickness

    Enter Thickness 2 mm. Orbit above the opening to inspect the walls and floor. If the cavity is rejected, reduce the thickness and read the task message.

  4. Apply the cavity

    Click Apply Shell or press Enter. The outside dimensions remain the same while the inside becomes hollow. The remaining floor is part of the solid.

  5. Edit the stored thickness

    Select the Shell history item and change Thickness to 3 mm in the inspector. Compare the smaller cavity, then undo to restore 2 mm. Save and reopen the project to inspect the retained feature.

Over to you

A small exercise

Open the top of the 15 mm block with a 2 mm Shell. Compare it with a 3 mm Shell, then restore the original thickness.

What you should see

At 2 mm, the rectangular cavity is 156 × 92 mm and 13 mm deep. The outer block stays 160 × 96 × 15 mm, with a 2 mm floor and side walls.

Things to look out for

  • The face you click is removed. Clicking a different supported face changes the opening.
  • A Loft or an already rounded, pocketed or hollow edited body is not valid for this workflow. Begin with the supported planar block.
Check your understandingDoes Shell shrink the outside of the block

No. This inward Shell keeps the outside and removes material inside it. Increasing Thickness makes the cavity smaller while leaving the outside dimensions unchanged.

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Go deeper in the knowledge base

Instructions checked against the Cadivari 0.3.0 source and knowledge base on 2026-09-16. Lesson revision 1.