# Subtract tool selects bodies, but does not work

**URL:** <https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501>\
**Category:** Modeling Questions\
**Created:** [July 23, 2022, 4:48pm UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501 "2022-07-23T16:48:13Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![LNXGUY](https://avatars.discourse-cdn.com/v4/letter/l/e480ec/32.png) [@LNXGUY](https://discourse.shapr3d.com/u/LNXGUY)\
**Post date:** [July 23, 2022, 4:48pm UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/1 "2022-07-23T16:48:13Z")

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I have selected the two bodies within the .stl model and the “done” button never appears.  
I clearly do not understand how this works. The tutorials and forum search have not helped.  
Please explain how to use this or some other feature to simply remove a few surfaces from this file.

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**Author:** ![Stephen](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/stephen/32/16350_2.png) [@Stephen](https://discourse.shapr3d.com/u/Stephen)\
**Post date:** [July 23, 2022, 5:30pm UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/2 "2022-07-23T17:30:55Z")

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Welcome LNXGUY. Without seeing a screenshot of your project, it’s hard to advise. One thing with subtract that new users of Shapr should check, such as original bodies being kept and making it look like subtract didn’t work. Check your list of objects and untick them one by one to see if they are obscuring a subtracted item.

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<div class="post-metadata">

**Author:** ![LNXGUY](https://avatars.discourse-cdn.com/v4/letter/l/e480ec/32.png) [@LNXGUY](https://discourse.shapr3d.com/u/LNXGUY)\
**Post date:** [July 23, 2022, 5:48pm UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/3 "2022-07-23T17:48:54Z")

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Where do I see a list of objects?

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<div class="post-metadata">

**Author:** ![Stephen](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/stephen/32/16350_2.png) [@Stephen](https://discourse.shapr3d.com/u/Stephen)\
**Post date:** [July 24, 2022, 2:28am UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/4 "2022-07-24T02:28:31Z")

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![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/d/a/da14895be54ee43b204c98d7eb90ca90b233de9d.jpeg)

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<div class="post-metadata">

**Author:** ![LNXGUY](https://avatars.discourse-cdn.com/v4/letter/l/e480ec/32.png) [@LNXGUY](https://discourse.shapr3d.com/u/LNXGUY)\
**Post date:** [July 24, 2022, 3:04am UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/5 "2022-07-24T03:04:04Z")

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The surfaces I want to remove are part of the main body of the object. When I select any of the surfaces, the entire body is highlighted.

There must be another tool to remove the vertices and surfaces individually. I have spent too much time on this project already, so I’ll just find another model and go from there…

Thanks

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**Author:** ![KPeter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/kpeter/32/7644_2.png) [@KPeter](https://discourse.shapr3d.com/u/KPeter)\
**Post date:** [July 26, 2022, 10:50am UTC](https://discourse.shapr3d.com/t/subtract-tool-selects-bodies-but-does-not-work/20501/6 "2022-07-26T10:50:18Z")

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Hey! STL, and overall mesh bodies have their limitations in a CAD software. In Shapr3D you have a limited toolset that can be applied to them, let me share the article about this topic:

> **[Can I modify mesh files in Shapr3D?](https://support.shapr3d.com/hc/en-us/articles/360024315354-Can-I-modify-mesh-files-in-Shapr3D-)**
>
> Save your mesh data in an STL file, and import it into Shapr3D.
> You can use the mesh data as a reference for your design with solid bodies, or modify it with boolean tools (Intersect, Union, and Su...

Instead of mathematical faces for example they have a group of polygons that are aligned to form the shape of a face, but they cannot be selected as a group. This is why the whole body selection is the only way to select meshes.

The Subtract and any other Boolean tool is a different case. First, the mesh has to be perfectly closed. If there is a small opening or an error in the file, it will be considered as an open body (Sheet body) and booleans cannot be applied.  
Many times, despite being a closed body, some of the edges or vertices may intersect with the edges/vertices of the other bodies involved in the Boolean which can also make the tool fail. In that case, please move one of the bodies just a tiny bit and give it another try.