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Boat Fender Line Guide

The rule of thumb is to use the largest diameter line you can when hanging a boat fender. Too small a line can cut through a vinyl fender eye like a knife, and larger diameter lines create a stronger connection. Having a better connection between the line and the fender will help keep your fenders working when you need them, in challenging docking situations, and using too small a line diameter voids Polyform's warranty.


Boat fender line attachment example, demonstrating proper fender line thickness
When boat fender lines are too thin they can cut through the fender ropehold as demonstrated in this image


Our preference is to use a looped connection with eyed fenders, keeping in mind hole through middle fenders like the HTM will work differently, (HTM Section). A looped connection with a fender eye allows a boater to use a lighter line, which most find easier to handle, while also making a stronger thicker connection to the fender eye. We recommend a splice, like our spliced lines here, or a bowline to make the loop in the fender line. When tying a fender to the boat or dock there are many methods and most work well, but it is common to use two half hitches or a clove hitch. If tying to a cleat a belay looped connection through the cleat or a cleat hitch are common.

Doubled or Looped Fender Connection

Line Recommendation Chart

A-0 0.6 " 1/4 "
A-1 1" 1/2"
A-2, A-3, A-4 1.125" 1/2"
A-5 1.25" 5/8"
A-6 1.5" 5/8"
A-7 2" 5/8"
F-1, F-02 0.7" 3/8"
F-2, F-3, F-4, F-5 0.9" 3/8"
F-6, F-7, F-8, F-10 1" 1/2"
F-11 1.1" 1/2"
F-13 1.2" 1/2"
G-1 0.375" 1/4"
G-2 0.5" 1/4"
G-3 0.625" 3/8"
G-4, G-5 0.75" 3/8"
G-6 0.875" 3/8"
HTM-1, HTM-2, HTM-3, HTM-4 0.625" 1/2" (Straight Piece of Line)
LD-1, LD-2, LD-3, LD-4 1" 1/2"
NF-3 0.625" 3/8"
NF-4, NF-5 0.75" 3/8"
S-1 0.5" 1/4"

Fender Lines on Hole Through Middle (HTM) Boat Fenders

Our HTM fenders work best with a 1/2 in. diameter line. You'll need a little more line than an eyed fender because you'll pass the line through the entire fender and you'll need a stopper knot on the end. In general we find the following line lengths work for most boats, but keep in mind your needs may be different.


Model Number HTM-1 HTM-2 HTM-3 HTM-4
Approximate Line Length 8' 9' 11' 13'