The crocodile shears was an instrument of torture

Torture

Torture is the act of inflicting severe pain as a means of punishment, revenge, forcing information or a confession, or simply as an act of cruelty. Throughout history, torture has often been used as a method of political re-education, interrogation, punishment, and coercion...

 used in late medieval Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and typically reserved for regicide

Regicide

The broad definition of regicide is the deliberate killing of a monarch, or the person responsible for the killing of a monarch. In a narrower sense, in the British tradition, it refers to the judicial execution of a king after a trial...

s, viz., those who attempted (and, perhaps, succeeded) to assassinate the king. Made of iron, the shears were based upon the concept of pincers, but instead of standard jaws or blades ended in a pair of hemicylindrical blades that, when closed together, formed a long, narrow tube. The insides of the blades were generously lined with teeth or spikes. After being heated red-hot, the crocodile shears were applied to the penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

, which, once exposed to sufficient tension, was torn from the prisoner's body; or, at the least, was severely mutilated.