The tribox, also called the Penrose rectangle or Penrose square, is an impossible figure that is the generalization of the Penrose
triangle from a triangle to a square. Similar -gonal figures can also be constructed for (Elber).
The figure above shows three impossible figures: the ambihelical hexnut in the lower left-hand corner, tribox in the middle, and impossible
fork in the upper right.
-gonal figures can also be constructed for 
(Elber).
