Just a little update.... Note that even if I turn the "hierarchy selection" option off for the Union tool, it still returns an error (hence only the body would be selected, not everything in the group): select -r |Body|Body ; select -tgl MouthShape ; { string $Selection1[]; $Selection1[0] = "BodyShape"; string $Selection2[]; $Selection2[0] = "BodyShape"; $Selection2[1] = "MouthShapeShape"; performBoolean 0 0 $Selection1 `currentCtx`; }; nurbsBoolean -ch 0 -nsf 1 -op 0 |Body|Body MouthShape ; // Error: boolean1 (Boolean Node): NURBS shell union failed. // // Error: explodeNurbsShell1 (Explode Nurbs Shell Node): Not a valid NURBS shell. // // Error: Command nurbsBoolean failed. Open Script Editor for details. // Again, any help would greatly be appreciated! I have tried searching the forums and Google. Problems with the Boolean tool seem to be commonplace, and I have read the most common reasons why the boolean tool fails, but I still haven't figured out what the source of my issue could be.