I bought three for my home office wall. They look really nice. There is a metal wall frame attached to the wall and the shelf slips over 2 arms on the frame. In the package are 8 Molly screws. A hole is drilled and a plastic insert is tapped into the hole. The frame is placed over these plastic inserts and then screws are used to attach it to the wall. This assumes you are attaching to wall board not studs. I tried to find out thru customer svc what size hole was needed and the only respnse I got was "All the parts should be in the package". I could not make the ones provided in the package work to my satisfaction. I would suggest you throw away the mollys that come with the shelf and head for your local H/W store and buy some that really work. 
which is what I did..
You will also do better with help in the install process for assuring everything is level.

Despite the minor problems I would recommend these shelves.