Understanding Boat Slips

Boats lined up in a harbor at sunset


nerffjones/Getty Images

There are many terms for parts of a boat, the way a boat is operated, and the facilities used to store and service a boat. Wow, it’s a lot to learn and many of the people you encounter expect you to know all of these things.

If you want to get a good start in the marine industry, a recreational facility is a great place to start. For the best chance of getting one of these jobs, you should know something about boat slips and dockage. An administrative person can fill a couple of sentences with enough terminology to confuse anyone who is more familiar with dry land than open waters. This can happen when you first start out your marine career adventure. It will also occur when you venture out to neighboring ports as you become more versatile.

Of course, you know your own home base marina and slip configuration, but can you understand questions marina staff might ask while traveling? Is the slip appropriate for your needs? On which side will you tie up? What tying fixtures are present? What kind of improvements need to be made?

Don’t worry it’s all fairly easy to understand.

Dock Structure

Large dock facilities are made up of one or more main docks connected to a face wall on shore. They come in two types, fixed and floating. Floating docks are usually connected to shore with hinged ramps which allow the docks to rise and fall with tides or changing water levels. Fixed docks are firmly attached to the shore and to support structures that are anchored underwater.

The main docks project out from the face wall and each main dock hosts many smaller and narrower docks called finger piers. These finger piers divide the slip areas and provide a way to walk from the boat to the main dock.

At the end of each finger pier and along the main dock are tall posts called piles. One or two extra piles also divide the area between two finger piers. These piles are only for tying, they don't carry a finger pier. Rarely, a slip will have a finger pier on each side of the slip space, but most facilities use the more efficient single side variety.

Tying up the Boat

Those two middle piles and the finger piers, with their piles, form a rectangle. This is the space where your boat should remain under all conditions. To assure it stays in position, it needs to be tied properly.

There will be a few different places to tie the four standard dock lines, plus some tying fixtures for extra lines needed in windy or stormy conditions. A boat is very secure when all eight lines are properly rigged and tied.

The names of the lines describe their position and function. The port and starboard bowlines connect to large loose rings at the front corners of the rectangle. The port and starboard stern lines connect to the outer pile and the pile at the end of the finger pier. This is secure, but the boat will still twist side to side and could strike the stern against the pier of pile in strong winds.

To eliminate the twist, spring lines are attached to the stern cleats and either run forward and tied to the cleat in the middle of the finger pier, or all the way forward to the rings where the bowlines are tied.

This process can be repeated with spring lines from the bow in the most extreme weather.

Bumpers and other padding can customize a dock to protect a specific boat. Sometimes large rollers are added to guide boats into slips where space is tight.

The classic mariner's book "The Ashley Book of Knots" is still in print and makes a great addition to any bookshelf for the history lessons alone, and you will learn many knots and splices as well.

Away From Home Port

If you are traveling and visit a marina, you can rent a transient slip. A transient slip is one that is rented regularly or it may be a slip which is vacant for a week because the regular tenant is also out traveling. Most marinas have a provision which allows them to rent any slip which is going to be vacant for more than a couple of days. If you find yourself putting another boater in someone’s regular slip be sure and leave it as it was found.

Once a boater requests a slip to fit the length and beam of the boat, as well as the amount of time needed, you should record the information. Then let the boater know the number and location of the slip and whether it is a port or starboard side tie up. This means that the finger pier will either be located on the port or starboard side. This is where someone can secure the boat while setting up other temporary lines.

The finger pier will have cleats which are shaped like a short and wide capital letter T. There are usually three or four with one on each end of the pier and at least one in the middle. On fixed construction docks it’s okay to just tie up to the finger pier unless the weather is very bad. If bad weather strikes you will need to move the boat away from the pier to avoid damage from rubbing.

Temporary dock lines are just like your permanent lines on a sailor's home dock but the lengths will be different so four lines half the length of your boat, and four lines the length of your boat should be in every boat inventory. Having a few extras around is a good idea in case one is lost, damaged, or left behind by the visitor.

Shore Power Ratings

Shore power comes in two sizes, one for regular boats and one for very large boats with lots of power requirements. A twenty-amp connection is equivalent to one standard 120-volt household outlet. For boats with full-size galleys or combination heating and air conditioning units, you will need a 240 volt, fifty amp connection, and appropriate power cord. Not all slips have both options so be sure to find out what power option is needed. It's also a good idea to know how someone might describe the plug configuration if they don't know the rating.


Ashley, Clifford W. "The Ashley Book of Knots." 1st edition, Doubleday & Company, 1993.

Was this page helpful?