Sydler's Dissection of a Pyramid into a Prism

This Demonstration is a dynamic illustration of lemma 20 from:
V. G. Boltyanskii, Tretja Problema Hilberta, Moscow: Nauka, 1977 p. 131.
Translated by R. A. Silverman as Hilbert's Third Problem (New York: John Wiley & Sons, Inc., 1978).