“…In some fortuitous situations, the necessary and sufficient conditions coincide. We avoid the wide array of sophisticated algebraic techniques for solving packing problems [1,2,9,10,30,32,33,35] in favor of more elementary combinatorial methods. 15 10 12 16 (a) (b) Figure 3 (a) P?rtition-and-pack strategy to tile a 37 x 32 rectangle, (b) Any 6 x 1 rect angle encloses a net charge of ?6, 0, or +6…”