Parallelepipedal solids which are on the same base and of the same height, and in which the extremities of the sides which stand up are on the same straight lines, are equal to one another.
Proof
The two parallelepipeds can be decomposed into congruent prisms via
XI.28 and I.34 applied repeatedly; the equality is the 3D analogue
of I.35 (parallelograms on the same base between the same parallels).