Revit API Element Image mirrorelement

Some Terms face, plane, and UV are involved here. They have not been clarified yet and are recorded for the time being. [Transaction (transactionmode. Manual)]
[Regeneration (regenerationoption. Manual)]
Public   Class Firewall firewall wall: iexternalcommand
{
Public Result execute (externalcommanddata upload data, Ref   String MSG, elementset elements)
{
Uidocument uidoc = Using data. application. activeuidocument;

Transaction TS= NewTransaction (uidoc. Document,"Http://revit.5d6d.com");
TS. Start ();

Reference=Uidoc. selection. pickobject (objecttype. element,"Select a wall");
Wall=Uidoc. Document. getelement (reference)AsWall;
Firewall wall (uidoc. Document, wall );

TS. Commit ();

Return Result. succeeded;
}
Private   Void Firewall wall (document DOC, wall)
{
Reference = Hostobjectutils. getsidefaces (wall, shelllayertype. Exterior). First ();
Face = Wall. getgeometryobjectfromreference (reference) As Face;
UV bboxmin = Face. getboundingbox (). min;
Plane plane =   New Plane (face. computenormal (bboxmin), face. Evaluate (bboxmin). Add ( New XYZ ( 10 , 10 , 0 )));
Elementtransformutils. mirrorelement (Doc, Wall. ID, plane );
}
}

From: http://revit.5d6d.com/thread-1274-1-1.html