This section is from the book "Popular Law Library Vol1 Introduction To The Study Of Law Legal History", by Albert H. Putney. Also see: Popular Law-Dictionary.
In addition to the requirements of military service, all persons holding land by knight service were subject to certain incidental obligations. At first these were merely for the purpose of protecting the lord's right to the military service, but they continued long after the military service had closed, and became great sources of hardship to the tenant. These incidents may be briefly summarized as follows:
Aids were extraordinary payments which tenants were obliged to pay on certain occasions; by Magna Charta these occasions were limited to three, to ransom the lord, to knight his eldest son, and once to marry his eldest daughter.
Relief was the payment which an heir or tenant must make to the lord upon succeeding to his estate. In the twelfth century the relief for a knight's fee was fixed as 100 s.; for socage land at one year's rent; with no fixed sum for baronies and grand serjeanties.5
Heriots were originally the horses and arms which the lord had lent to his vassal and which he had the right to take back at his death; later the right was that of the lord to take the best chattel of the deceased tenant.
The right of wardship was the right of the lord to act as guardian of an infant heir of one of his tenants, receiving the profits of the estate and only paying for the present support of the heir out of such income. As the land was given in return for military service, there was, in theory, no great injustice in the lord receiving the income during such time as the tenant was unable to render such services.
The greatest hardships involved in any of the so-called incidents of the feudal tenures, were those arising out of the right of the lord to control the marriage of his tenant. Originally this right was extremely limited, extending only to the right to prohibit the marriage of a vassal heiress with a party objectionable to the lord. As the husband of such heiress would have to render the military services due for the land, the lord had an interest in preventing such land falling into the hands of one of his enemies. Later this right of control was extended over the marriage of the male heir, and by a still later and further extension the lord was not only permitted to prohibit a marriage to an objectionable party, but even to pick out a wife or husband for such heir or heiress, whom they were obliged to marry under penalty of a heavy fine. For a long period the right of marriage with an heir or heiress was freely and openly sold by the feudal overlords.
5 Glanville, I. X. C. 4.