# Splitting closed polysurface creates strange shape

**URL:** <https://discourse.mcneel.com/t/splitting-closed-polysurface-creates-strange-shape/72272>\
**Category:** Rhino for Windows\
**Created:** [October 3, 2018, 3:29am UTC](https://discourse.mcneel.com/t/splitting-closed-polysurface-creates-strange-shape/72272 "2018-10-03T03:29:26Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![abrahamwechter](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/abrahamwechter/32/479869_2.png) [@abrahamwechter](https://discourse.mcneel.com/u/abrahamwechter)\
**Post date:** [October 3, 2018, 3:29am UTC](https://discourse.mcneel.com/t/splitting-closed-polysurface-creates-strange-shape/72272/1 "2018-10-03T03:29:26Z")

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Splitting the black closed polysurface with the red surface produces a strange shape at the bottom-looks like a bug to me, or please explain.  
Using Version 6 SR8

 ![cutaway%20block%20trimmed%20before%20split](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/3/9/39f9ef161330d5acf7009a2c5979eb6a53605fc7.jpeg)  
 ![cutaway%20block%20trimmed%20after%20split](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/b/9/b95a54b2d464b920cf7e41c5628b1f24bd34ff14.jpeg) [cutaway block trimmed.3dm](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/7/a/7a81245de3ce6f1019340ffb638ad1278123acae.3dm) (150.5 KB)