Dock Lines 101: Thickness, Braids, and FAQs!

As a boat owner, it’s important to understand a few basics about dock lines to make sure that docking your boat is a breeze.

To start, consider whether these lines will be permanent or transient.  Will you be docking in your permanent location every time or not?

There are a few ways that you can customize your lines if you know that you will be docking in the same place every time. For example, having lines that are the exact length you need as well as having loops on both ends of the line can make for a safe and tidy dock.

If you are willing to put in a little bit of sweat equity, consider splicing your own lines to create loops exactly where you need them. These splicing fids are a great tool for most rope sizes and their stainless steel design makes for easy work.

What number of dock lines do I need?

At a minimum, any boat will need a minimum of four lines. If you are only docking at home you will need at least one bow line and one stern line.

Your bow and stern lines prevent either end of your boat from pulling away from the dock.

Depending on your slip, you may need additional lines for your bow or stern. A few factors like exposure to elements such as wind or currents should be considered.

If you plan to use your boat to travel, this may justify having more.

When traveling, you may have to dock on either side, so having two bow lines and two stern lines will make for convenient and less chaotic docking.

You will also need two spring lines. Spring lines are placed in the middle of the boat and cross on a shallow diagonal. These prevent your boat from moving forward or backward. These should hold the boat tight to the dock.

How to calculate the optimal thickness of dock lines

The standard diameter for dock lines is ⅛ of an inch for every 9 ft of boat.

The minimum should be ⅜ of an inch regardless of boat size. Generally the larger the rope the easier it is to handle so many boaters tend to round up when selecting lines.

What’s the optimal dock line length?

As a general rule for traveling, you will want your bow and stern lines to be at least ⅔ the length of the boat.

For example, if you have a 20 ft boat your lines should be approximately 13 ft.

If you are docking at home you can measure your current lines to get an accurate length for each line.

Spring lines should be the length of your boat but this is something you can customize if you will only be docking at home.

Adjusting cleat location and the length of these lines can also make your boat more secure. Consider how you can locate cleats and lines to create an opening for boarding where there are no tripping hazards.

The optimal material for dock lines: nylon

The go-to material for dock lines is nylon. Its stretch and durability make it perfect for dock lines.

Nylon lines are also the perfect weight for tossing should the occasion arise.

Polypropylene ropes are great for when you need a rope to float, but they deteriorate quickly in the sun.

Braid types and colors

For the most part, there are three types of nylon lines.

  • Three-strand twisted. This is the most affordable nylon line and the easiest to splice. It is composed of no inner core but simply three nylon lines twisted together.
  • Braided. This is composed of a smooth inner core and a braided sheath. It is easy to handle.
  • Double braided. The double braided line type is braided on both the inside and the outside of the rope. For this reason, they will be the most durable.

Does dock line color matter?

When it comes to the color of dock lines, it’s simply a matter of personal preference as opposed to any type of color-coding system.

Consider that white lines will show dirt and dark lines will be subject to UV damage and fading.

Some people choose to use one color for the bow and stern lines and another color for the spring lines. This can simplify communication during docking and undocking.

How long do dock lines last?

Regardless of your efforts, dock lines will usually need to be replaced every 3-5 years depending on your setup and exposure to the elements.

Rain, mildew, and salt water can take their toll on lines. Eliminating buildup as it appears can help improve the lifespan of your lines.

How to clean dock lines

Cleaning them with water and soap every season can help your lines last longer. Vinegar can help break down mold and mildew. During your annual cleaning, lines should be inspected for chafing or tearing.

There are solutions for preventing chafing. Rubber sleeves or polyester sleeves can be easily cut and simply slid over the line to reduce wear and tear on lines.


While docking your boat is really a craft that is honed over time, assessing the condition of your lines and preparing for every potential situation will ensure your boat is safe and secure.

Keeping the dock clean with coiled lines or draping them over the cleat will prevent tripping and also make you look like a seasoned boater!

While you’re at it, be sure to check out the post I wrote on Dock Cleats 101, for everything you need to know on that front 🙂

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