A codicil is a legal document that is used to make changes or additions to an existing will. It is a separate document that is attached to the original will and must be signed and witnessed in the same way as a will. Codicils are typically used to make minor changes to a will, such as adding or removing beneficiaries, changing the distribution of assets, or updating executor appointments. It is important to consult with a lawyer when creating a codicil to ensure that it is done correctly and in accordance with state laws.