These bookcases are connected with a "bridge" that serves as more shelf space as well as a surface for mounting task lighting and crown rope lighting. All shelves are fixed for extra strength. The material is ash (think baseball bats) with Italian bird's eye maple veneer for the door panels and main surfaces. The unit is about 10' long and 7' tall, and was made to enhance an Ash Desk that I built four years ago--the wall unit will darken to match the desk in a few years.