# Anyone know what might be stopping this solid from boolean union-ing?

**URL:** <https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684>\
**Category:** Rhino for Windows\
**Tags:** windows\
**Created:** [October 17, 2026, 10:52am UTC](https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684 "2026-10-17T10:52:13Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![John\_Swiers](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/john_swiers/32/758685_2.png) [@John\_Swiers](https://discourse.mcneel.com/u/John_Swiers)\
**Post date:** [October 17, 2026, 10:52am UTC](https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684/1 "2026-10-17T10:52:13Z")

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Whenever I try to union the top object into the bottom one, the bottom one vanishes. I assume I’ve got something wrong with the object, but can’t work out what. Anyone got any thoughts?

[union error.3dm](https://discourse.mcneel.com/uploads/short-url/f8s3xcxij9UrCTBv0k46Dgryumb.3dm) (90.8 KB)

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**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [October 17, 2026, 11:24am UTC](https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684/2 "2026-10-17T11:24:27Z")

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![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/0/e/2/0e2bd4380faed213fa836782cf47e05eb1f253ee.png)

the upper part is not solid, it has naked edges.  
see properties → open polysurface  
find naked edges → \_showEdges  
the normals point inwards → \_dir

my approach:  
\_explode  
delete unneeded, inner surface  
\_join  
worked:  
(rhino 8 on mac)  
[union error\_tom\_p\_fix.3dm](https://discourse.mcneel.com/uploads/short-url/710w5eOUUtAxoW0hUQCIE4uhiIp.3dm) (3.0 MB)

kind regards - tom

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**Author:** ![John\_Swiers](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/john_swiers/32/758685_2.png) [@John\_Swiers](https://discourse.mcneel.com/u/John_Swiers)\
**Post date:** [October 17, 2026, 11:41am UTC](https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684/3 "2026-10-17T11:41:00Z")

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Thanks for the explanation! I have a lot to learn about making custom shapes. This helped a lot.

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**Author:** ![Lagom](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/lagom/32/767418_2.png) [@Lagom](https://discourse.mcneel.com/u/Lagom)\
**Post date:** [October 17, 2026, 12:46pm UTC](https://discourse.mcneel.com/t/anyone-know-what-might-be-stopping-this-solid-from-boolean-union-ing/223684/4 "2026-10-17T12:46:45Z")

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You could also build your object from simple NURBS surfaces and join the surface once ready for exporting. No booleans needed.

[union error.3dm](https://discourse.mcneel.com/uploads/short-url/uelhNvZ1c6VKkARDMsNzjTW7Q8f.3dm) (2.2 MB)