Unpaid military service, usually of forty days' duration, owed to lord or king in return for tenure of land. (Frame, Robin. Colonial Ireland, 1169-1369, 144) Related terms: Knight's Fee / Knight
Initially the knights rewarded with grants of land had to perform knight service to the king and his barons but over a few generations this military service was separated from the holding of land and the military service was commuted to a money payment known as “shield money” (scutage) and with these fees the king was able to pay fighting men.