expand the full dialog.
( In NX the name to stitch surfaces together to a larger sheet body is called "sew". "Join" is a feature to merge two faces that had a dividing edge between them.)
Body type = Sheet will let you sew to a sheet body.
Why do you want this result ?
- The surface math is the same but there is no "solid body-definition", no logic on what is inside or outside of the faces, no volume, no density etc.
Regards,
Tomas