Dowels can be very handy for supporting shelves from the sides. If shelf ends are notched, you can build a room-dividing-bookcase by cutting a standard 4 by 4 to reach from floor to ceiling (where it is attached with an L-shaped bracket) and running dowels through at varying heights to hold the shelf ends. Or, a back cleat can be combined with pins or dowels on the sides of a bookcase to form a sturdy support.
There are many different types of metal fixtures available for bookshelves. Brackets, braces, and angle irons can be purchased in a wide variety of sizes, shapes and styles (including ornamental designs) for attaching open shelves to either back or end supports. Metal brackets add strength where a heavy load is to be placed on shelving.
Wood Shelving Brackets
For adjustable shelving - a great way of eliminating waste space - wall standards with notches 13mm.apart can be purchased along with special brackets to fit them. They are available either for shelves supported from the sides or from the back. For end support, pair of the 20mm. wide standards and two brackets for each side of each shelf is needed. For back supports, one pair of wall standards will do, unless the shelves are extra long. Shelves are supported by rungs. Notch ends of shelving boards to fit snugly between supports. Height of shelves is easily changed. Bookcase can be dismantled.
You can choose almost any wood for bookshelves, provided it can stand the dead weight of the volumes it will hold. Commonly used types are 25mm. by 300mm. fir and particle board and 20mm. plywood. Many lumberyards carry 1-inch thick bookshelf stock that has a rounded front edge.
Bookshelf space should be a minimum of 23cm. high and 21cm. deep for books of average size. Larger volumes may require a shelf 30cm. deep and 30cm. high. Width usually depends on the number of books you have to shelve. The highest shelf should be no more than 2 meters off the floor.