How do the peasants help the knights

In 'Life in a Medieval Castle' Frances and Joseph Gies write:

'Through the twelfth century the tendency towards exclusivity grew in the knightly class. Frederick Barbarossa and probably other sovereigns forbade peasants to become knights or to carry sword or lance; and by the thirteenth century the knightly aristocracy was in theory a closed caste: set apart from the rest of society. "Ah God! how badly is the good warrior rewarded who makes the son of a villein a knight!' warns the romance Girart de roussillon. But the poet's admonition is itself evidence that villeins did indeed become knights in the twelfth century, and in the thirteenth century the process was almost commonplace. The chief reason wsa the growing wealth of the merchant class. A grandfather might found a business, a father expand it, a son inherit a fortune. such a son might purchase estates in the country from which he could draw an aristocratic name; he could afford expensive entertainment and bribes to great lordss, and be knighted if he chose. Thenceforard his descendants were knights. Rather than seeking to suppress the custom, the great lords, in defiance of such edicts as Barbarossa's, took the sensible course of regularising it by charging a fixed fee for knighthood.

At the other end of the economic scale, again despite all prohibitions to the contrary, many a poor soldier won knighthood through valour in the service of a lord. Despite this double-ended openness of the knightly class, it nevertheless retained a distinct caste rigidity. Its newest members, like parvenus of every age, copied or even excelled the hauteur of their older brothers in aristocracy.'

Source(s): Life in a Medieval Castle by Frances and Joseph Gies