 2PRHS                                                      Menu: (POLYG) PRISM
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 Creates a hollow rectangular prism or two (2D) rectangular nested polygons,
 given a base plane and two opposite corners.

         1. * (CHAR) plane of base rectangle (x-xy,y-yz,z-zx)<x>
         2. * (POINT) first point
         3. * (POINT) opposite point
         4. * (NUM) "wall" thickness (greater than 0)
      for option `x':
         5. * (NUM) height of prism
      for options `y' or `z':
         5. * (NUM) width of prism
      for all options:
         6. * (Y/N) positive prism ? <y>

 Description:
 This command creates a set of two nested rectangular polygons or a hollow
 rectangular prism based on the polygons.



 Specify a base plane: x  xy plane (the default), y  yz plane or z  xz plane
 and define the two extremes of the base rectangle. Specify the "wall"
 thickness and the height (or length) of the prism (you may enter 0 for a 2D
 polygon). Enter `y' for a positive prism (the default), or `n' for a negative
 one. You are prompted to create more prisms until you enter another command.

         Example: \2prhs x 0 0 0 4 4 0 0.2 3 y

 Result: A 4 by 4 by 3 rectangular pipe with a "wall" thickness of 0.2 units is
 created having its lower-left corner at the point 0 0 0.
