Parcel Post

Designer unknown, made by and computer analysis done by Bill Cutler 1979.
(wood box and 18 wood pieces, 4.8" by 6.8" by 1.7" thick)

A box of inside dimensions 18 x 28 x 6 units into which must be placed 18 two unit thick pieces of sizes 4x9, (2) 5x9, 5x18, 5x21, 6x7, 6x10, 6x13, (2) 7x8, (2) 7x13, 7x18, 8x18, 9x11, 9x13, 10x11, and 11x11. Cutler's analysis showed four solutions (not counting rotations and reflections), all placing the 4x9, 6x7, and 6x13 pieces on end. Here is one of them, from the sheets that came with the puzzle (copyright by and courtesy of Bill Cutler).

top layer
middle layer
bottom layer

Exchanging the middle and bottom layers gives a second solution, and these two solutions each have an alternate version by exchanging the 7x18, 5x21, 6x10 pieces on the top layer with the 7x13, 5x18, 10x11 pieces on the middle layer.