By the second half of the fourteenth century, in addition to forces raised on the basis of common service and feudal obligations, money contracts of "bonds" or "bands of manrent", similar to English indentures of the same period, were being used to retain more professional troops, particular men-at-arms and archers. In practice, forms of service tended to blur and overlap, and several major Scottish lords brought contingents from their kindred. These systems produced relatively large numbers of poorly armoured infantry, usually armed with 12–14 foot spears. They often formed the large close order defensive formations of shiltrons, able to counter mounted knights as they did at Bannockburn, or infantry assault as at Otterburn in 1388, but vulnerable to arrows (and later artillery fire) and relatively immobile, as they proved at Halidon Hill in 1333 and Humbleton Hill in 1402.