Watson taught the boys carpentry, joinery and gardening. It is also used as a softwood timber in stair treads and joinery. The durable heartwood is used as timber in joinery and high-class furniture. It is used in the manufacture of furniture, joinery, veneers, luxury flooring, and boat building. Solid hardwood joinery tends to be expensive compared to softwood. This, along with a knowledge of joinery, are the basis of timber frame building. The use of denser wood led to much finer work, including more elaborate joinery. There are similar fittings for both sweat and solvent joinery. These include biscuit joints and pocket hole joinery. The screwed butt joint is common in both frame and carcase joinery. Complex construction techniques such as joinery began in the early dynastic period of ancient Egypt. It is used in joinery and sheetmetal operations. Router bits come in hundreds of varieties to create either decorative effects or joinery aids. Subsequently, it reverted to making joinery and doors for the building trade. Several bicycle frames have been made of bamboo tubes connected with metal or composite joinery.