# Student needs help with boolean difference

**URL:** <https://discourse.mcneel.com/t/student-needs-help-with-boolean-difference/28842>\
**Category:** Rhino for Windows\
**Tags:** boolean\
**Created:** [January 29, 2016, 10:49pm UTC](https://discourse.mcneel.com/t/student-needs-help-with-boolean-difference/28842 "2016-01-29T22:49:31Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Rob4](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@Rob4](https://discourse.mcneel.com/u/Rob4)\
**Post date:** [January 29, 2016, 10:49pm UTC](https://discourse.mcneel.com/t/student-needs-help-with-boolean-difference/28842/1 "2016-01-29T22:49:31Z")

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I have a closed poly-surface and I am trying to cut a small rectangle into it using Boolean difference and every time I attempt it, it fails. Both my professor and multiple other students have looked at it and attempted to cut it. The rectangle and the poly surface both check out and with no issues. I need help figuring out what it is that keeps causing it to fail so I can fix this as well as having learned hoe to do this so I can help others.  
-Thanks, Robby[.usb V2.3dm](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/9/3/93df1e459bf4516d2ae36e9864b6f884d2aefff8.3dm) (167.8 KB)  
(the part I need help with is the half dome with the box inside it, if that makes sense.) thanks again

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**Author:** ![pascal](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pascal/32/479395_2.png) [@pascal](https://discourse.mcneel.com/u/pascal)\
**Post date:** [January 29, 2016, 10:53pm UTC](https://discourse.mcneel.com/t/student-needs-help-with-boolean-difference/28842/2 "2016-01-29T22:53:13Z")

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Hi Rob - Boolean operations do not work between curves and surface objects directly - Extrude the rectangle into the solid, and then Difference.

Also, your sphere part has internal surfaces - that may be the problem you are running into.  
Explode the object and remove the inner faces (work in Wireframe mode to see these more easily) then join the rest so there is just the outer ‘shell’.

![](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/8/9/89e6ceb534e6b06fa129f9a63ed1d5e1f98f6342.png)

-Pascal

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**Author:** ![schultzeworks](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/schultzeworks/32/488974_2.png) [@schultzeworks](https://discourse.mcneel.com/u/schultzeworks)\
**Post date:** [January 29, 2016, 11:00pm UTC](https://discourse.mcneel.com/t/student-needs-help-with-boolean-difference/28842/3 "2016-01-29T23:00:40Z")

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Booleans can be tricky. I have a [free video](http://www.lynda.com/Rhino-tutorials/Troubleshooting-solids-Booleans/133324/153928-4.html) on trouble-shooting tips you might want to check out.

If you want to watch the rest of this [Rhino 5 course](http://www.lynda.com/Rhino-tutorials/Rhino-5-Essential-Training/133324-2.html), you need to be a [lynda.com](http://lynda.com) member. Here’s a link for [10-days free](http://www.lynda.com/trial/dschultze).