When you think of adjustable furniture, a shelf bookcase isn't usually the first thing that comes to mind. But it's actually ...

In most modern homes, any adjustable shelves or cabinets have metal shelf pins set inside conveniently spaced holes. Before the accoutrements of modern life, like easily replicated metal parts ...

And shelves are typically adjustable, so you can change shelf heights to accommodate small items like canned goods and tall ...