The help says that sew can also be used to sew solid bodies.
I think that sew unites the bodies or sheets and also extends them within a tolerance, and must be non-disjoint along all the edges.
Another difference is that the Sew operations are more 'tolerant' than simple Booleans. By that we mean that if face edges match WITHIN the Modeling Distance tolerance, the sew operation will still join the bodies and will use one of the edges as the 'edge of record' as it were.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA Siemens PLM: UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.