How to create "shell" between two faces? Loft failed many times

[zhangyehua1996]

I'm trying to connect two objects together, so it will be like a box. I have two semi-open boxes and I want to make them one box by creating a "shell" that connects two parts. Both parts are 3mm thick so the thickness of the shell should be 3 as well. However, no matter how I twist Loft settings, I always getting an ugly non-hollow body. Is it possible? Or what are the alternative solutions? Thank you

[dsouzasujay]

Hi @zhangyehua1996 ,

Can you Attach prior designs that you have already completed in Fusion 360?  Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?