A more thorough explanation:

Definition: Knight's fee is a term used in history to refer to the amount of land that was required to be held by a person in order to be obligated to provide knight-service. The size of the land varied from less than a hide to more than six hides.

Example: If a person held a knight's fee of two hides, they were required to provide the lord with two fully equipped knights for a certain period of time each year.

Explanation: This example illustrates how the amount of land held by a person determined their obligation to provide knight-service. In this case, the person holding two hides of land was required to provide two knights, while someone holding less land may only be required to provide one knight.