Choose dock lines and fenders for your boat and the actual berth. Boat length is a starting point; dock height, hull shape, exposure and the available attachment points affect the setup.
Use the manufacturer's sizing guide
Polyform publishes fender choices by boat length and application. Its guide is a starting point rather than a guarantee for every berth. Identify the series and model before comparing physical dimensions.
Samson's recreational marine selection guide provides dock-line length and diameter choices. Read the chart for the exact rope product, then check your boat and dock hardware.
Open Polyform's fender guide
Open Samson's dock-line selection chart
Polyform sizing examples
Selected examples from Polyform's general chart—not universal dimensions for other brands:
| Boat length | Example fender models |
|---|---|
| 15–20 feet | G-3 or NF-3 |
| 20–25 feet | F-1, G-4 or HTM-1 |
| 25–30 feet | F-2, G-5 or HTM-2 |
| 30–35 feet | F-4, G-5 or HTM-3 |
Polyform recommends at least three fenders for docking, with coverage near the bow, widest hull area and stern. Adjust placement to the actual contact surface and berth. Read its full chart for additional model choices and applications.
Record these measurements first
| Fenders | Dock lines |
|---|---|
| Boat length and hull shape | Boat length and exact rope construction |
| Contact height at the dock | Boat-cleat and dock attachment locations |
| Dock face, pilings or another boat | Actual line route and working length |
| Protected berth or exposed mooring | Diameter compatible with the cleats |
| Space to hang and store each fender | Chafe points and required protection |
Match the fender to the contact
Do not buy only by color or the word “large.” Check the manufacturer's dimensions and intended application, then confirm that the fender can stay between your hull and the surface it must protect.
At your berth, identify the likely contact zones and the expected changes in water level. Plan the attachment and adjustment before leaving the boat. A fender that misses the contact point does not provide the protection you intended.
Match dock lines to the layout
Make a list of each required line and its attachment points. Distinguish the boat's routine berth setup from a temporary dock visit. Use actual measurements to choose lengths; one prepackaged length may not serve every position.
Confirm that the line diameter works with the boat's cleats and the dock hardware. Check the rope maker's product instructions for handling, splicing and inspection. Keep a replacement record so the next order matches the existing setup.
Before you leave the boat
- Check that fenders remain at the intended contact points.
- Inspect each line along its route and at hardware contact points.
- Check the setup against the berth's tide, water level and exposure.
- Ask the marina or a qualified operator to review unfamiliar docking arrangements.
Routine sizing guidance is not a storm mooring plan. Use a separate preparation plan for severe weather.
Compare docking equipment
Shop docking essentialsUpdated October 2026. This guide explains selection and planning; use the exact equipment instructions for installation.