The document describes 10 different types of screws and bolts used in engineering. Wood screws are used for wood and have a tapered point. Machine screws are used to fasten metal parts and have threads but no point. Thread cutting machine screws can self-tap threads in metal. Sheet metal screws are fully threaded and pointed for use in sheet metal. Self-drilling screws can drill and tap their own hole in metal or wood. Hex bolts have a hexagonal head and threads to be used with nuts or tapped holes for fastening wood or metal. Carriage bolts have a smooth rounded head and square neck to fasten metal to metal or wood. Lag bolts have a hexagonal head and wood threads for connecting