Hi Pilou,

> here click 5 click 6 don't give the same result than click 1 click 2 ! not ok !

Each set of points makes a connection between the edges, and if you make connections that cross each other they won't be able to be used and all the connection information will be ignored.

So that's what looks like happened in your second image there, if you imagine a line connecting each pair of points, you've got some lines crossing each other rather than making an ordered set of connections between the edges.

The main use of add sync points is for more curved shapes so you can control how they connect together.

- Michael