Extrusion is an easy method of 3D geometric model creation from the 2D planar sketch. First the geometry is defined in XY plane. Then all planar objects - in QuickField they are vertices, edges and blocks - are assigned the numbers, which represent the height levels of the corresponding object along the Z axis. Thus the planar node becomes the vertical edge of 3D structure, planar edge transforms into the vertical surface, planar block becomes the horizontal face. Space surrounded by horizontal and vertical surfaces defines the 3D body within.