Chock
A chock guides a mooring or towing line so it runs fair from winch to shore without chafing on deck edges, carrying no holding load itself since that sits on the bitts or the winch drum brake behind it.
What to check on a Chock.
6 models from Wärtsilä in Chock. Below: the full model list.
What a chock actually does
A chock is a fitting through which a mooring or towing line passes so the line runs fair from a winch or bitts to the shore or another vessel, without chafing on deck edges or the ship's own structure. It carries no load itself in the way a bollard or bitt does; its job is to guide and constrain the line's direction while the actual holding load sits on the bitts or winch drum brake behind it.
Legend
- deck
- chock (smooth bore)
- bitts
- mooring line
- ship side / bulwark
- to quay
- line does not load the chock; load is held at the bitts
Main components and types
Closed chock
A fully enclosed oval opening, the most common type, preventing the line from jumping out under a shifting lead angle.
Open (roller or Panama) chock
An open-top fitting, often fitted with a roller, sized and positioned per Panama Canal Authority requirements on vessels that transit the canal, since canal mooring lines are handled by shore locomotives at angles a closed chock cannot accommodate.
Read the full guide
Universal chock
Combines a fairlead opening with an integral bollard or bitt point in one casting, saving deck space on vessels with limited mooring deck area.
Roller insert
Where fitted, reduces line friction and chafe damage, at the cost of an extra wear part that needs its own bearing inspection.
Selection and sizing
Selection follows the mooring line's safe working load and material - synthetic fibre ropes need generous bearing radii to avoid heat damage from friction, wire ropes need a harder, smoother bearing surface - plus the deck layout's actual lead angles from winch to chock to the mooring point ashore. Panama or universal types are fitted where trade pattern or class notation calls for them, not as a default choice.
Regulations and class
Chocks fall under the vessel's approved mooring arrangement, assessed against class equipment number calculations and, for canal transits, against the specific fitting positions and dimensions the Panama Canal Authority publishes for its mooring procedure. There is no periodic statutory survey specific to chocks beyond the general condition checks covered in deck equipment and mooring system inspections.
Typical faults
- Sharp or corroded bearing surface - cuts into synthetic line fibres or scores wire rope, a leading and entirely preventable cause of mooring lines parting under load.
- Cracked casting at the base - repeated snap loading from a line running out fatigues the fitting where it is welded or bolted to deck, and a failure here releases the line's full load suddenly.
- Seized roller - a roller-type chock that no longer turns behaves like a fixed chock, defeating the reason it was fitted and accelerating chafe.
- Wrong chock for the lead angle - a line running at a steep angle through a chock sized for a fair lead concentrates wear on one edge and shortens line life significantly.
What to look for in a supplier
- Bearing surface finish and radius matched to the mooring line types actually carried aboard.
- Casting material and load rating documentation tied to the vessel's equipment number, not a generic size chart.
- Panama Canal Authority compliant dimensions and positioning data where the vessel transits the canal.
Run a hand along the chock's bearing surface at every deck round - a nick too small to see is still large enough to start cutting a synthetic mooring line under load.
Models in this type.
The best-documented model of each manufacturer first, then the next — 6 of 6 models in Chock. Every row links to full specifications, documents and service notes.
Manufacturers.
All 9 manufacturers with models of Chock. Names with a manufacturer page open it; the others open a search across the full library.
All manufacturersAlso in Deck Fittings & Hardware.
The other equipment types in this category.
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Three things people ask first.
Is Chock data free?
Yes. Every model page, every guide and every datasheet for this type is readable without an account. An account adds saved searches and requests, nothing is taken away.
My model is missing — what now?
Send us the nameplate. We identify it by hand, add it to the library, and if you need a part or a service, the request is already on our desk.
Can you source a Chock part?
Yes. Tell us the manufacturer, the model and what you need — a person reads every request and replies by e-mail.