Prosthetics are basically artificial "replacements" for a body part. Dentures are a prosthetic for someone who lost all his or her teeth. It helps the person be able to chew (masticate) food and...
Since the 1950s more than 80 models of prosthetic heart valves have been developed and used. More than 60,000 valve replacements are performed annually in the United States
A model aeroplane is used for presentations and testing. Model planes are also used for fun. They are used model-plane clubs, aeroplane company headquarters and studios. (Bedroom, in my house)
The ancient Germanic tribes and the ancient Scandinavians used runes as an alphabet. Prior to that, they used runes for magic purposes, such as casting lots (divination) and spells of protection.