A crank is an arm attached at a right angle to a rotating shaft by which circular motion is imparted to or received from the shaft. When combined with a connecting rod, it can be used to convert circular motion into reciprocating motion, or vice versa. The arm may be a bent portion of the shaft, or a separate arm or disk attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod (conrod).

Guido da Vigevano or Guido da Vigevano da Pavia was an Italian physician and inventor. He is notable for his sketchbook Texaurus regis Francie, a catalog of military equipment, and his Anothomia Philippi Septimi, an illustrated work on dissection. Each provides insight into the state of medieval technology and medicine. As an inventor, Guido can be regarded as a distant forerunner of later Renaissance artist-engineers like Taccola, Francesco di Giorgio Martini and Leonardo da Vinci. As an anatomist, Guido documents the practices of the fourteenth-century Bolognese school and its esteemed doctor Mondino de Luzzi.