What is the difference between adjustable and fixed shelves in a bookcase?

Adjustable shelves use a pin-and-shelf-standard system that allows shelf height to be repositioned in 1"–2" increments to accommodate items of different heights. Fixed shelves are permanently attached during manufacture. Commercial office bookcases use adjustable shelves on all interior positions and fixed top and bottom shelves. At OfficeFurniture2go.com, all our bookcases feature adjustable interior shelves — call 1-800-460-0858 for configuration details.