Hi Karsten (KMRQUS) and Michael,

and thank you very much for your help.

Unfortunately, this isn't the first time that i forget to check the topology of the edges, before continue to try to do what i want to achieve...

Then, i thank you Karsten for reminding me the existence of the Merge command :)

Now, it's not my intention to bore, you or Michael, with strange and unverifiable issues,
but i observed a strange behavior that occurs to the Shell command,
in relation with the position of the mouse pointer and the zoom level,
and camera position while confirming the input of the selected area for that command.

I made this tests on the same object indicated by Karsten, but without first executing the Merge edge command.

Well...sometimes the Shell command works and sometimes not,
depending on the zoom level and camera position in 3d view and
if the MOUSE POINTER IS OR NOT OVER THE SELECTED AREA THAT ACT AS STARTING POINT for the shell command.

Or, at least, this is what i'm observing.

Sad to say that i'm not able to reproduce this issue in a stable way.
If any of you want to try, please give me the chance to verify what i'm saying.

Is any of you is aware of this behavior ?

The zoom level in 3d view or the camera position and angle has some sort of influence to the Shell or other commands ?

Thank's for all and have a nice evening,

Marco.