Select the wall and then right mouse click.
CONNECT > Trim to roof/shell.
Select the shell to trim to and then select the portion of wall to keep.
Or you can use Solid Element Operation.
This is assuming you want to remove part of the wall above/below the shell.
Otherwise select both wall and shell then right mouse click.
CONNECT > Merge Elements.
This will keep both elements intact but will create the join.
Barry.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10