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From SofTutor for AutoCAD 3D - Using UCS To Draw 2D Lines In 3D
Topics covered in this video are:

Copying Multiple Elements In 3D Duplicate UCS Demo Omitting The Z value When Drawing With 2D Tools XY User Coord Demo Drawing Lines In 3D @ At Symbol Mech Demo Using UCS To Draw 2D Lines In 3D Icon XYZ User Coord Demo