Abstract: A binder with a security lock feature having front and back cover panels connected by a spine, and a page-holding mechanism attached to the spine on the inside of the binder for releasably holding pages in the binder. The page-holding mechanism includes a post assembly having a plurality of posts extending generally transversely of the spine at locations spaced longitudinally of the spine for holding pages in the binder. Each post is made up of a pair of interengageable post elements separable to permit pages to be inserted into and removed from the binder. The post assembly is movable between a first position in which the post elements of each post are interengaged and inseparable, and a second position in which the post elements are separable. A latching member is movable between a latching position for latching the post assembly in the first position and a release position for enabling the post assembly to be moved to the second position.