An Anchor is a heavy implement that is dropped to the sea bottom to keep a ship or boat from drifting. It is attached to a line or chain cable and is carried on deck or stowed in a suitable receptacle so that it can be used quickly. When dropped, the anchor provides holding power either by digging into the sea bottom or by sheer weight.
The earliest anchors were probably heavy stones tied to ropes. In Egyptian tombs, ship models have been found with grooved or perforated anchor stones, some of which are shaped like a T. Crooked stocks or wooden frames weighted with stones (killicks) have been used for centuries.
It is believed that iron anchors were first forged about 575 a.d. in England. By 1600, iron anchors had a long shank (vertical bar), two sharply pointed straight arms at right angles to the shank, a large wooden stock (crosspiece) for turning the arms in a soft ocean floor, and an iron ring for attaching the mooring cable. This design was a forerunner of the all-iron Admiralty anchor, which had curved arms with pointed flukes (flattened ends of the arms), a shank, a stock, and a ring. By 1852 the Admiralty anchor had gained wide acceptance by the British navy. The folding-fluke anchor was introduced in England in 1818, and the folding-fluke, stockless anchor was patented before 1840. The mushroom anchor appeared in use in 1859.
The Admiralty anchor, although no longer used on large ships, is still in use for small boats. It has great holding power in a soft bottom, but it is awkward to handle, and one fluke always projects above the sea bottom where it may foul the anchor cable. The folding-fluke, stockless anchor is used by large ships and naval vessels. It can be stowed compactly, and both flukes dig into the sea bottom, minimizing the risk of fouling the cable. This type of anchor is often carried in an opening in the bow called a hawsehole. The mushroom anchor continues to be useful for small craft. It is particularly effective in soft, muddy bottoms. Modern anchors usually are made of cast or forged steel rather than iron.
Newer anchor designs include the Danforth and Northill anchors. Tests have shown that these types have a much greater ratio of holding power to anchor weight than the older types. These newer anchors are used for sailboats, small powerboats, and large cabin cruisers. However, the selection of an anchor depends on many factors, including the type of boat, the size and weight of the boat, the type of bottom, and wind and weather conditions.