Abstract: Disclosed is a mounting structure for mounting a horizontal insertion loading data storage drive in a data storage library having downwardly inclined shelves. A bracket mounts the data storage drive, and support bars are mounted in parallel in the data storage library and support the bracket on each side at a downwardly inclined angle. Thus, the horizontal insertion loading data storage drive is mounted at the downwardly inclined angle to receive data storage media from a robot accessor at the angle of the downwardly inclined shelves. The mounting structure support bars are parallel slides which slidably support the bracket at the downwardly inclined angle. A ratchet bar is mounted in the library at the downwardly inclined angle, and has a plurality of ratchet holes in the downwardly inclined direction. A latch is mounted on the bracket for engaging the ratchet holes of the ratchet bar to support the bracket and data storage drive against sliding on the support bar slides.