Books
Bundling together old hardcover books can create shelving supports that are safer to work with and that are more easily adjustable than cinder blocks. You can adjust the height of your shelves by adding or removing more books. Used hardcover books can be purchased inexpensively, and you can use duct tape to bind the books together.
Old Computer Cases
Because computer technology tends to change frequently, people find themselves buying a new computer every few years. Over time, the amount of used metal computer cases can start to pile up. If you know people who have old computer cases they are not using, ask if you can have them for your new shelving unit. The metal cases will provide a sturdy support structure for your shelves, and the front panels will create an interesting design look.
Crates
Storage crates can help you build a stable shelving unit and add more storage space to your shelving unit as well. The ideal crates to use are made from metal with hard plastic bases. These can withstand more weight than the plastic storage crates, but plastic storage crates can be used for shelves that are not expected to hold more than books or smaller items. You can stack large and sturdy wooden crates to act as shelving units on their own. Attach the wooden crates to each other with twine to ensure they do not fall.
Glass Jars
Large glass jars can be used as decorative and effective shelving supports. For smaller shelves you can use mayonnaise jars or canning jars. Larger shelves would require larger storage jars. The jar tops are not necessary. You can put marbles or any other kind of decoration inside the jars to add to their stability as well as to enhance your shelves appearance. Use at least two jars per side to enhance stability.