Armor changed over time. Until about the middle of the 13th century, knights wore shirts and leggings of mail. After that plates made of hardened leather, and then steel, were added to protect the most exposed areas of a knight's body. This mail shirt is made up of 250,000 interlocking metal rings and must have taken a long time to make. Mail was strong and flexible. You can’t even push a pin through the most tightly woven mail.