Tugboats are usually seen, and imagined, in the harbors and smaller waters of the world, docking an undocking ships.  These are the harbor boats and their job goes basically like this.

The tug's captain moves the tug alongside the ship.  The tug's crew sends up a large line that the ship's crew makes fast to the ship.  Then the tug's crew fastens that line to the tug.  once everything is in place, the docking pilot, who is aboard the ship directing the operation, calls out orders over the radio and the tug maneuvers as necessary to help the ship into or out of her berth.

The equipment on deck is fairly easy to keep straight.  To do this job, these items are needed:  A stout line of about four inches in diameter, a smaller messenger line, used to haul the heavy docking line up to the ship's deck, and an even smaller heaving line, to get the messenger up to the ship's deck first.

Here is a view of the bow of a tug that is getting ready to dock a ship.  The job can be done from the stern and "made up" as well, but we're going to talk about the most common way that tugs move ships.  The large docking line is obvious.  To the left, coiled on deck is the messenger line.  This line is easily handled by the crew of the tug and the ship and can be taken to a capstan and hauled up under power without breaking like the smaller heaving would.  Sometimes the docking line must be pulled dozens of feet up to the ship and the weight of a wet line gets heavier as it leaves the deck- much heavier.

To get the messenger up to the crew of the ship, the tug's crew throws a heaving line.  The heaving line is fastened to the messenger and the ship's crew can bring it up by hand no matter how high or far away they are from the tug.

 The knot at the end of the heaving line is called a Monkey's Fist Knot.  The extra weight on the end of the line makes the line sail through the air for great distances.  Many boatmen pride themselves on the length and accuracy of their throws.

Here is a boatman making his throw. It looks as though he must reach a height directly over his head.

You can see the messenger line on deck just behind him.

Here the tug's crew is fastening a messenger to the end of another line to go up.  There are many configurations that the pilot may request to move the ship depending on the conditions.  Sometimes more than one line and different types of lines are employed.

Here is the line going up.  In the foreground are the H-bitts that will be used to fasten the docking line to the tug.

Whether on the stern or on the bow, the H-bitts are the most important piece of deck furniture on the tug, and the crew knows many ways to make a line onto them.

Here are different type of bitts.  The set above are in a triangular configuration and the set to the left have a power capstan built onto them to help bring long docking lines in tight.

No matter what they look like, the important job they do remains the same.

Once the line is up and both ends are fast, the crew takes a short break while the captain and the docking pilot do the rest.

Here is a tug positioned at the bow of the ship it is moving.  This is the most common job of the ship docking tug in harbors.

This is the docking pilot.  He is in radio contact with the tug's wheel house.

He observes the movement of the ship from the bridge wings and directs the ship's captain in the use of his engines, while directing the tug's captain to pull the ship with his line or push against it with his fender system (also known as pudding or puddening).

As he gives a order to the tug, the tug can reply with his whistle to acknowledge the order as understood.

A forward order gets one toot, and a backing order gets two toots.  Stopping orders get one toot just a little longer than normal.

Here is  a small tug with a line up on the stern of a ship.  Sometimes harbor tugs are employed this way to help a ship steer while transiting winding rivers.  This is a job that is going to the more modern ship docking modules and tractor tugs, so popular these days.

There are many jobs that harbor do to move ships, barges, and large marine equipment.  The job remains the same.  Get to the job, put up a line, and move around with power and grace combined.

The last whistle signal the crew hears is the long toot followed by two short ones.  "Bring your line in."  After the line is back aboard the tug the crew can straighten up the lines and decks and then get ready for the next job, or the trip back to the yard for a break.