Knots, Bends, and Hitches

TL;DR — Every licensed mariner must know eight foundational knots: bowline, clove hitch, cleat hitch, sheet bend, square knot, figure-eight, rolling hitch, and anchor bend. Knots are chosen for ease of inspection and release after load; splices are stronger but permanent. USCG Boatswain Manual Ch. 1 §1.3

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What the Rule Says

Marlinespike seamanship is the discipline that governs the use, care, and maintenance of all rope, fibre line, wire rope, and synthetic line aboard a vessel. USCG Boatswain Manual Ch. 1 §1.1 It is a core competency for any OUPV or Master 100 GT candidate, and the exam tests it directly.

The Eight Basic Knots

The USCG Boatswain's Mate Manual identifies eight knots every mariner must know. USCG Boatswain Manual Ch. 1 §1.3 Each has a specific purpose, and the exam will test whether you can match the knot to its correct application.

1. Bowline The bowline forms a fixed, non-slipping loop at the end of a line. It is one of the most important knots in seamanship because the loop will not tighten under load and can be untied after heavy strain. USCG Boatswain Manual Ch. 1 §1.3

2. Clove Hitch The clove hitch secures a line to a spar, piling, or ring quickly. It is a temporary fastening — reliable under a steady, perpendicular load but prone to slipping if the load direction changes or the line is alternately loaded and unloaded. USCG Boatswain Manual Ch. 1 §1.3

3. Cleat Hitch The cleat hitch is the standard method for securing a line to a cleat. It begins with a round turn around the base of the cleat, followed by figure-eight turns, and finishes with a locking half-hitch. It is the knot used daily for dock lines and halyards. USCG Boatswain Manual Ch. 1 §1.3

4. Sheet Bend The sheet bend joins two lines of unequal diameter. The larger or stiffer line forms the bight; the smaller line passes through and around it. A double sheet bend adds a second turn for extra security when the size difference is significant. USCG Boatswain Manual Ch. 1 §1.3

5. Square Knot The square knot (reef knot) joins two lines of equal size and is used primarily for bundling or reefing — not for joining lines under heavy load, where it can capsize into a slip knot. USCG Boatswain Manual Ch. 1 §1.3

6. Figure-Eight The figure-eight is a stopper knot tied in the end of a line to prevent it from running through a block, fairlead, or cleat. It is bulkier and easier to untie after load than an overhand knot. USCG Boatswain Manual Ch. 1 §1.3

7. Rolling Hitch The rolling hitch secures a line to a spar or to another line under lengthwise strain — that is, when the pull is along the axis of the object rather than perpendicular to it. The extra turn on the side of the load is what prevents slipping. USCG Boatswain Manual Ch. 1 §1.3

8. Anchor Bend (Fisherman's Bend) The anchor bend attaches a line to an anchor ring or shackle. Two round turns pass through the ring, and the working end is tucked back under both turns. It is the preferred knot for this application because it will not slip under the cyclic loading that an anchor line experiences. USCG Boatswain Manual Ch. 1 §1.3

Knots vs. Splices

The manual draws a clear distinction: knots are tied for ease of inspection and untying after load; splices are stronger and permanent. USCG Boatswain Manual Ch. 1 §1.3 Any knot reduces the breaking strength of a line at the knot point. A properly executed splice retains a far greater percentage of the line's rated breaking strength and is the preferred method wherever a permanent termination or joining is acceptable.

Line Materials in Context

Understanding why you choose a particular knot also requires knowing the line material you are working with. Modern small-vessel operations use predominantly nylon and polypropylene synthetic lines. USCG Boatswain Manual Ch. 1 §1.1

Nylon is the most common dock and anchor line because of its high strength, excellent shock absorption, and resistance to mildew. USCG Boatswain Manual Ch. 1 §1.2 Its elasticity — the same property that makes it ideal for anchor rodes and dock lines — means that knots in nylon can loosen slightly as the line stretches and recovers. Inspect knots in nylon lines regularly.

Polypropylene floats, which makes it useful for applications where the line must remain on the surface (e.g., a heaving line or a water-ski tow), but it has lower strength than nylon and degrades under UV exposure. USCG Boatswain Manual Ch. 1 §1.2 Wire rope is reserved for standing rigging and heavy-load applications. USCG Boatswain Manual Ch. 1 §1.1

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Why It Matters on the Exam

OUPV and Master 100 GT written exams include Deck General questions that require you to identify the correct knot for a described situation, or to identify a knot from a description of its construction or purpose. The examiners test three things:

1. Knot-to-application matching. You must know which knot is correct for a given task. The most commonly tested pairings are:

• Joining two lines of unequal size → sheet bend USCG Boatswain Manual Ch. 1 §1.3
• Fixed loop that will not slip → bowline USCG Boatswain Manual Ch. 1 §1.3
• Attaching a line to an anchor ring → anchor bend USCG Boatswain Manual Ch. 1 §1.3
• Securing a line to a spar under lengthwise strain → rolling hitch USCG Boatswain Manual Ch. 1 §1.3
• Stopper knot to prevent running through a block → figure-eight USCG Boatswain Manual Ch. 1 §1.3

2. Knots vs. splices. Exam questions may ask which method is stronger or which is preferred for a permanent connection. The answer is always the splice. USCG Boatswain Manual Ch. 1 §1.3

3. Line material properties. Questions may describe a scenario — anchor line, dock line, heaving line — and ask which material is most appropriate. Nylon for dock and anchor lines; polypropylene where flotation is needed; wire rope for standing rigging and heavy loads. USCG Boatswain Manual Ch. 1 §1.1 USCG Boatswain Manual Ch. 1 §1.2

Marlinespike seamanship also connects directly to mooring operations. The lines you rig — bow line, stern line, forward spring, after spring, and breast lines — are only as reliable as the knots and hitches securing them to cleats, bitts, and pilings. USCG Boatswain Manual Ch. 2 §2.1 A cleat hitch improperly finished without the locking half-hitch can work free under the cyclic loading of a vessel surging at a dock.

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Common Pitfalls

Confusing the sheet bend with the square knot. Both join two lines, but they are not interchangeable. The square knot is for lines of equal diameter and light bundling duty only. The sheet bend is the correct choice when joining lines of unequal size or stiffness. Using a square knot to join two lines of different diameter under load risks the knot capsizing. USCG Boatswain Manual Ch. 1 §1.3

Confusing the clove hitch with the rolling hitch. The clove hitch is for perpendicular loads on a spar or piling. The rolling hitch is for lengthwise (axial) loads. Exam distractors will swap these two. The key discriminator is the direction of the load relative to the object the line is hitched to. USCG Boatswain Manual Ch. 1 §1.3

Assuming knots are as strong as splices. They are not. The exam may present a question asking which connection method retains more of the line's breaking strength. The splice is always the stronger, permanent option; the knot is chosen when the connection must be inspectable and releasable. USCG Boatswain Manual Ch. 1 §1.3

Misidentifying nylon's weakness. Nylon loses approximately 10–15% of its strength when wet and stretches under load. USCG Boatswain Manual Ch. 1 §1.2 Exam questions may describe a line that has been in service as a dock line and ask about its properties. Do not confuse nylon's UV resistance (good) with polypropylene's UV resistance (poor). USCG Boatswain Manual Ch. 1 §1.2

Overlooking the anchor bend for anchor applications. A candidate who defaults to a bowline for attaching a line to an anchor ring will be wrong. The anchor bend is the correct knot for that specific application. USCG Boatswain Manual Ch. 1 §1.3

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Quick Check

Q1 — You need to join a 5/8-inch nylon dock line to a 3/8-inch polypropylene heaving line. Which knot is correct?

Sheet bend. The sheet bend is the correct knot for joining two lines of unequal diameter. The larger or stiffer line forms the bight; the smaller line passes through and around it. A square knot is not appropriate here because the lines are of different sizes. USCG Boatswain Manual Ch. 1 §1.3

Q2 — A line is rigged to take a lengthwise strain along a spar. Which knot prevents the line from sliding along the spar's axis?

Rolling hitch. The rolling hitch is specifically designed to resist axial (lengthwise) loads on a spar or another line. The extra turn on the load side is what prevents slipping. A clove hitch would be incorrect here because it is designed for perpendicular loads. USCG Boatswain Manual Ch. 1 §1.3

Q3 — Which is stronger: a properly tied bowline or a properly executed eye splice in the same line?

The eye splice. Splices are stronger than knots and are permanent. Knots are chosen for ease of inspection and untying after load, not for maximum strength retention. USCG Boatswain Manual Ch. 1 §1.3

Q4 — You are attaching a nylon anchor rode directly to the anchor ring. Which knot should you use?

Anchor bend (fisherman's bend). Two round turns pass through the ring, and the working end is tucked back under both turns. This knot resists the cyclic loading an anchor line experiences and will not slip free. A bowline, while forming a secure loop, is not the preferred knot for direct attachment to an anchor ring. USCG Boatswain Manual Ch. 1 §1.3

Q5 — A line must be prevented from running through a block. Which stopper knot is preferred, and why not an overhand knot?

Figure-eight knot. It is bulkier than an overhand knot, seats firmly against the block, and — critically — it can be untied after being loaded, whereas an overhand knot tends to jam tight and become extremely difficult to release. USCG Boatswain Manual Ch. 1 §1.3

Q6 — Which synthetic line material is most susceptible to UV degradation, and what is its primary advantage over nylon?

Polypropylene degrades under UV exposure. Its primary advantage over nylon is that it floats, making it suitable for applications where the line must remain on the water's surface. Nylon, by contrast, offers higher strength and superior shock absorption but does not float. USCG Boatswain Manual Ch. 1 §1.2