A more thorough explanation:

Definition: A legal document that allows someone other than the owner of a security to transfer ownership of that security to a third party. It is also known as a stock power or bond power.

Example: Let's say John owns 100 shares of Apple stock. He wants to sell those shares to his friend, but he can't be present to sign the necessary paperwork. John can use a stock/bond power to give his friend the authority to sign the paperwork on his behalf and transfer ownership of the shares to him.

Explanation: A stock/bond power is a useful tool for transferring ownership of securities when the owner is unable to be present to sign the necessary paperwork. It allows someone else to act on the owner's behalf and complete the transfer of ownership. In the example above, John uses a stock/bond power to give his friend the authority to sign the paperwork and transfer ownership of the Apple stock to him.