Boss (engineering)
In engineering, a boss is a protruding feature on a work piece. A common use for a boss is to locate one object within a pocket or hole of another object. For instance, some motors use a precisely machined boss on the front face to locate it on the mating part. Like a process on a bone, bosses on castings can provide attachment points or bearing surfaces. The term 'boss' when used in engineering can also relate to a finishing edge around (usually) a circular opening that allows the opening to locate onto, or within another opening thus  locating or joining two items together with a view to the location or joining being temporary or semi-permanent. A common everyday example of a boss is the housing of the rotation spindle in a washing machine drum, or on a cylinder lawn mower at the end of the cutting blade cylinder which may house a bearing set to allow the cylinder to rotate through one plane, but held firm in another plane. A boss can also be a brass eyelet on a sail. It is a generic term to describe an item designed to facilitate the use with, within , on or around another item whereby one cannot operate properly without the other. The word 'boss' is also often used to describe the end of a shaft on a boat to which a propeller might attach. A boss may also refer to a mounting feature that will receive a screw or thread-forming screw. In computer-aided design applications, a boss is a feature used to describe a type of extrusion. The word boss comes from the Middle French word "", which means protuberance.