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A mooring line is a thick rope or cable which is used to tie a watercraft in place. Usually multiple mooring lines are used on the same vessel to distribute the stress, and to act as redundant systems in case a mooring line snaps. Mooring lines may also be known as hawsers. A number of materials can be used to make a mooring line, and most marine supply companies carry an assortment of options which can be customized as needed.
Mooring a vessel requires some coordination. The mooring lines need to be thrown to shore, but they are sometimes too heavy and awkward to be thrown easily, especially in the case of lines used on large ships. As a result, sailors use an attachment called a heaving line, a lightweight cord which can be tossed to shore. People on shore can use the heaving line to pull the mooring line over so that the boat can be moored in place. With a very large ship, a large crew on land may be involved to coordinate the mooring process. For smaller craft, a single sailor can handle mooring independently.
Historically, mooring lines were made from natural fibers like hemp, which were braided and corded for extra thickness. Today, materials such as synthetic fibers and metal may be used. Wire mooring lines have a very high tensile strength, but tend not to be as flexible, and they can be hard on the hands. For this reason, some companies make mooring lines with a metal core and a synthetic wrapper.
These lines can be used to tie a boat in place on a dock, jetty, quay, buoy, or so forth. On the ship, there are multiple points of attachment which can be used for mooring lines so that they can be positioned in the best way possible. On shore or on the structure the ship moors to, similar points of attachment are available. The line is always neatly tied off to prevent it from slipping, and excess is coiled so that people will not trip.
One danger with mooring lines is that when they are subjected to high stress and pressure, they can snap. This poses a risk to navigation, because a ship could break free of its mooring and drift. It can also be dangerous to people, as a snapped mooring line can strike someone as it recoils, causing serious injuries or even death. For this reason, sailors are careful about the maintenance of their lines, addressing signs of damage and fraying promptly.
@irontoenail - I never knew that the name for those things was a bollard. I associate mooring lines with the knots that are used to tie them. Your line is only going to be as good as the knot used to secure it and not all of them come with the rope already formed into a loop.
We learned how to tie several of the most common rope knots for mooring when I was in the scouts and I've never forgotten them. It's surprising how often they come in handy, although I've never actually used them to moor a ship. Maybe one day I will.
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