Helllo!

Thank you BurrMan for tutorial! It works for me now)

Thanks Michael, it's more clear now for me. But still needs more time and practice to get it this type of workflow, after poly modeling

So, I fixed that places on my model. But after trying to apply same method to another parts, I faced with another issue: that new surface doesn't weld with geometry.

On screenshot - I marked hole in my mesh, and after trying to fix that on the right side ( and it didn't work) and after reopen file I get this wierd issue.
If I'm selecting and delete that surface, I get that (second screen shot). And Its hard to fix - some edges couldn't be deleted or separated.
I attached model file.
Thank you very much guys for help.

Hi Skyground, when you get that kind of stuff it usually means there is some kind of error in the trimming boundary of a surface, stuff like the trimming boundary is made up of edges that have a gap between them instead of touching end to end, or the boundary is self intersecting with edges crossing over each other. I'll take a look at your model and try to see what's going on there.

- Michael

Hi Skyground, one of the surfaces in that area doesn't seem to have a fully closed trim boundary on it:





I'll see if I can get it tuned up for you.

- Michael

There's also another couple ones where the trim boundaries are way far off from the actual underlying surface, something didn't go well with the retrimming.

- Michael

On a couple of those spots, after doing an extrude the surface should fit right in place and not need trimming, if you try to trim a surface with something that's right at edge of the surface leaving no actual surface area to trim away that could be the problem you ran into.

- Michael

Hi Skyground, I've attached a fixed version of your model, it needed the bottom face to be rebuilt and also a couple of surfaces in the left and right corners. Only one of them actually needed to be trimmed to go into place, the others I extruded to a snap point so the extrusion was the right size right from the start and could just be joined in directly.

- Michael

Hi Michael !

Thank you very much! I think I understand now little bit more)

Thanks for fixed file. I will continue to work on it

- Alex