The Metal Bookshelves are a set of tile entities added by GregTech 6. They are used to hold books, Thaumometers, Keys, cobblestone, and any other item with the tooltip "Can be placed inside a GT Bookshelf". Most of these items have a custom render while in a bookshelf, others are disguised as books. Each of the four shelves can hold seven objects. They can be made from different metals for aesthetic purposes, and can be dyed.