In terms of form follows function, a standard bookcase like the Billy shown below is a perfect design. It also uses the bare minimum amount of materials required to perform its function.

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An issue of materials waste, however, becomes apparent when you acquire a second unit and place the two side by side.

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That's because we now have two doubled-up sides where the units adjoin, where just one vertical could easily support the shelves on either side. There is more material used than necessary, added weight in shipping, more fuel burnt, and more to carry when it comes time to move house.

Frank Howarth, for whom efficiency in design and construction is always a priority, sought to solve this problem. Here's what he came up with:

The solution is as simple as it is clever. The weakest part of the I-shaped supports would be where the serifs are butt-jointed together. But the base stiffens up the bottom butt joints, and because the tops needn't support any weight and the structure is stiffened by the shelves, he can get away with nothing more than pocket screws. I also like that it was designed for eventual disassembly.

Ikea would do well to take a look. If they could overcome the barrier of educating consumers, they could conceivably offer a modular, expandable line of bookcases based on these repeatable verticals and an array of end-piece options, and save a fair bit of material in the process.