Ready-to-assemble furniture (RTA), also known as knock-down furniture (KD), flat-pack furniture, or kit furniture, is a form of furniture that requires customer assembly. The separate components are packed for sale in cartons containing assembly instructions and sometimes hardware. The furniture is generally simple to assemble with basic tools such as hex keys, which are also sometimes included. Ready-to-assemble furniture is popular with consumers who wish to save money by assembling the product themselves.