This shield developed from the larger medieval heater shield. As knight's body armour had become more effective the shield became less important for direct protection. No longer having to protect the body a smaller shield was easier to move in reaction to an opponents attack. This shield was more able to glance a blow and better body armour could stop any weakened glanced blows. With the body and face covered in a suit of armour no one could see who was who. Colours and devices painted on the shield were used to show who was in that armour. These designs were inherited but sometimes, after marriage, half the father's designs were added to half the husbands. With passing generations this practice became very complicated, so the laws of heraldry were developed.