A more thorough explanation:

An instrument of crime is an object that is made or adapted for criminal use or is commonly used for criminal purposes and is possessed under circumstances showing an unlawful purpose.

Examples of instruments of crime include:

• A lock-picking kit
• A ski mask worn during a robbery
• A crowbar used to break into a building

These examples illustrate the definition of an instrument of crime because they are all objects that are specifically designed or commonly used for criminal purposes. Possessing these objects under circumstances that suggest an unlawful purpose, such as carrying a lock-picking kit while attempting to break into a building, can result in criminal charges.