An anchor is a device attached to a boat or ship and cast overboard that keeps the vessel in a particular place by digging into the bottom. The word anchor comes from the Greek word meaning hook or crook. Prehistoric anchors held vessels in place simply by their great weight and bottom friction, and therefore consisted of a single, large stone or a basketful of stones. Sacks of sand also were sometimes used as were logs of wood loaded with lead. All of these primitive types are called deadweight anchors.

During ancient or Graeco-Roman times, anchors were made of iron and were given teeth or "flukes" to fasten themselves to the bottom. It is known that during Caesar's time a variety of anchor types and sizes were carried when extensive seafaring voyages were made. Each had its own particular use for certain conditions. During the Middle Ages, little...