A more thorough explanation:

Definition: “Four corners of an instrument” is a legal principle that states that the meaning of a document should be determined solely from the language used in the document itself. This means that any information that is not included in the document, such as the circumstances surrounding the document or the history of the parties involved, should not be considered when interpreting the document.

Example: Let's say that you signed a contract with a company to provide services for them. The contract clearly states that you will be paid $1000 per month for your services. However, the company later claims that they only agreed to pay you $500 per month. According to the principle of four corners of an instrument, the court would only consider the language used in the contract itself to determine the payment amount, and would not take into account any outside information or circumstances.

Another example: A lease agreement between a landlord and a tenant states that the tenant is responsible for all repairs and maintenance of the property. The tenant later claims that the landlord promised to take care of certain repairs. However, according to the principle of four corners of an instrument, the court would only consider the language used in the lease agreement itself to determine the responsibilities of the landlord and tenant, and would not take into account any outside promises or agreements.