Hi Chri,

""""""but i dont understand why deleting 26 edges erase the hole on the surfaces ?

This is untrimming a trimmed surface.

So things like that hole are represented by a trim boundary that has a type of label that says "hide inside"... the actual surface doesn't really leave.

MoI has a mechanism for untrimmimg a trimmed surface. That is done by selecting all the trim boundaries and deleting them to reveal the underlying surface.

In some cases you may want to copy and save the trim boundaries before untrimming. So if you need to retrim a particular part, you already have the boundary for the surface.