Barn Door Bookcases – IKEA Billy is a range of door frames and bookcases. The shelves that come in various sizes and colors. All the different parts can be mixed and matched to create a personalized bookcase system. Ikea produces several different types of doors for Billy’s rank. They have different finishes, colors, patterns, and materials, but all of them are attached to the Billy bookshelf rack in the same way. Ikea has pre-drilled holes in Billy’s pieces to make the job easier. Position the door hinge slots through the pre-punched holes in the Ikea Billy frame, with the arrow.