# How to make a border with lots of edges?

**URL:** <https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232>\
**Category:** General Discussion\
**Created:** [February 3, 2020, 8:25am UTC](https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232 "2020-02-03T08:25:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Mordokkai](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@Mordokkai](https://community.freefem.org/u/Mordokkai)\
**Post date:** [February 3, 2020, 8:25am UTC](https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232/1 "2020-02-03T08:25:25Z")

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Hi everyone,

At first I want to say that I’m not an expert neither in PDEs nor in FreeFEM. I would like to build a 2D mesh: the external border is a square (ez to do), but the internal border is a polygon with lots of edges. The examples I found in the documentation where always building a mesh from an explicit sequence of borders like:  
mesh Th = buildmesh(C01(-n) + C02(-n) + C03(-n) + C04(-n) + C05(-n));  
But in my situation, I can’t sum the borders like that since too much borders and I dont know before execution how many there will be.  
Maybe I didn’t see something, again I’m not used to FreeFEM 🙂  
Have a good day

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**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [February 3, 2020, 8:59am UTC](https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232/2 "2020-02-03T08:59:35Z")

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see 3.2.3 Multi-Border in the doc.