Knights were required to provide, of course, military service. That was, after all, their primary vocation. Their oath of fealty to a lord would include a promise to protect their lord’s life, honor, and property.
Besides fighting on horseback during battle, a knight might also do duty at the lord’s garrison, act as an arbiter or even a judge in minor grievances, and proffer advice and counsel to his master on a variety of issues. It was common for knights to be assigned administrative tasks such as garnering supplies.
In return, the lord would defend the knight and his family from their enemies, and avenge wrongs. The lord would grant fiefs of land, access to forests, rents from houses, and income from a plethora of sources such as mills and mines. The fiefs were given to support the knight’s family and military needs such as horses, squires, training, and additional stores.
Usually the fiefs were hereditary, and passed to the knight’s children, but not always. For example, if a knight was assigned as castellan (governor of a castle), the lord could take that fief away, particularly if there was rebellion in the knight’s family.
It was not uncommon for knights to swear fealty to more than one lord, acquiring more fiefs in the process. Many ministerales became wealthy by such devices, and tiptoed around conflicting oaths with difficulty. Lords were not always averse to such practices, as they could turn to their wealthy knights for financial support in waging war or providing ransom for kidnapped familae.
The penalties for breaking the knightly code were severe. Confiscation of fiefs was the customary punishment. Depending on the gravity of the offense, he could lose his wife, his children, and be cast an outlaw, whereby no one was allowed to assist him in any way.
On the other hand, lords who did not fulfill their duty suffered little consequence. If it was an ongoing problem or widespread across all of the lord’s retinue, rebellions did occur. Royal courts might have to be involved and that outcome usually was to neither parties’ benefit, but rather to the royal household itself. Thus, the incentive was to settle matters within the familae and maintain the peace.