# 2D boundary of a cube

**URL:** https://community.freefem.org/t/2d-boundary-of-a-cube/1119
**Category:** General Discussion
**Created:** [July 26, 2021, 1:25pm UTC](https://community.freefem.org/t/2d-boundary-of-a-cube/1119 "2021-07-26T13:25:27Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![simonenatipoltri](https://avatars.discourse-cdn.com/v4/letter/s/e19b73/32.png) [@simonenatipoltri](https://community.freefem.org/u/simonenatipoltri)
#### Post date: [July 26, 2021, 1:25pm UTC](https://community.freefem.org/t/2d-boundary-of-a-cube/1119/1 "2021-07-26T13:25:27Z")

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Hi there, I’ve constructed a cube in such a way

load “msh3”  
int[int] ll= [1,2,1,2,3,4];  
mesh3 Th = cube(20,20,20,label=ll);

how do I introduce a 2D mesh defined as one of the faces of the cube? Is it possible to use meshL Th1=buildmeshL(…) even if I’ve not used borders to construct the cube?

Thanks,  
Simone.

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<div class="post-metadata">

### Author: ![simonenatipoltri](https://avatars.discourse-cdn.com/v4/letter/s/e19b73/32.png) [@simonenatipoltri](https://community.freefem.org/u/simonenatipoltri)
#### Post date: [July 29, 2021, 10:32am UTC](https://community.freefem.org/t/2d-boundary-of-a-cube/1119/2 "2021-07-29T10:32:18Z")

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I solved with

int[int] llabs = [5];  
meshS ThS = extract(Th,label=llabs);