Single Flush Mount Hidden Knotty Alder Bookcase Door$? DESCRIPTION If you've ever dreamed of having a hidden door, but didn't want to deal with the hassle of building and installing one, you've come to the right place. Constructed with an MDF Core and Knotty Alder Veneer, our flush mount Bookcase Door arrives pre assembled and installs like a regular door! No special framing. No custom work. And our patented hinge system provides effortless operation even when fully loaded, up to 300 lbs. Now you can