Rope Seizings — Flat, Round and Racking: When and How to Use Each

Collection: Regenerative Materials | Series: Natural Ropes |

Subject: Three types of seizing, what each one is actually doing, and why Bushell uses two of them together on every shroud eye

The thing I kept treating as one thing

For longer than I should admit, I thought of seizings as a category rather than as several distinct things with different load-bearing geometries. A seizing was a binding of twine around two parts of rope, applied tightly, finished with a square knot or a few frapping turns. This understanding was adequate for casual ropework and insufficient for anything I actually needed to rely on.

The gap became apparent when I started working through Bushell's shroud eye specifications. He does not apply a seizing to a shroud eye. He applies a throat seizing followed by a quarter seizing, at specific positions, with specific dimensions for each, and he gives the reason for using two different types in sequence. Reading that, I realised I did not have a clear enough understanding of what a flat seizing does versus what a round seizing does, or why a racking seizing exists as a distinct type rather than as a variation of the others. What followed was the usual process — back to the sources, then to practice, then back to the sources with better questions.

The three types and the principle behind them

All three seizings share a basic structure: turns of small stuff wound tightly around two parts of rope, with the turns secured against slipping by a finishing method. The differences lie in how the turns are arranged and what loads that arrangement can resist.

Flat seizing is the simplest. The turns are laid alongside one another in a single layer, each touching the previous one, working from one end of the seizing to the other. The finished seizing is a band of parallel turns around the two rope parts. It resists forces that try to separate the two parts radially — pulling them apart sideways — but it has limited resistance to forces that try to slide the two parts past one another lengthwise, because the parallel turns have nothing to resist longitudinal slip beyond friction.

Round seizing adds a second layer of turns — riding turns — laid over the first layer in the spaces between the first layer's turns. The riding turns are fewer than the first layer turns, typically about half the number, and they sit in the valleys between the underlying turns rather than beside them. This second layer locks the first layer against spreading under load, and the crossing geometry between layers resists longitudinal slip more effectively than a flat seizing can. A round seizing is stronger in all directions than a flat seizing of equivalent width.

Racking seizing is different in character from both. Instead of parallel turns laid in one direction around both parts, the racking turns are figure-of-eighted between the two rope parts, crossing between them alternately on front and back. The crossing turns grip each rope part independently and resist the tendency of the two parts to slide past one another far more effectively than parallel turns can. Where flat and round seizings hold two parts together primarily through the compression of the turns around them, a racking seizing holds them together through the mechanical interlocking of the crossing turns.

The practical implication: use flat seizing where the load is primarily radial — where the two parts are being pulled apart sideways and you want to keep them together. Use round seizing where the load is more complex and you need resistance in multiple directions. Use racking seizing where the two parts are under loads that would slide them past one another — where the shear force between them is significant.

What Bushell does at the shroud eye

The shroud eye in lower rigging is the most structurally demanding seizing application on a traditionally rigged vessel. The eye must hold under the full load of the shroud — the mast's lateral support against wind pressure — and it must do so over years of service without creeping or failing progressively.

Bushell applies two seizings to every shroud eye: a throat seizing first, then a quarter seizing below it. The throat seizing goes on close to the stop that holds the two parts together while the seizing is applied, its turns laid from the stop toward the standing part of the shroud. The quarter seizing goes on four inches below the throat seizing, and it is flat rather than round — Bushell specifies this explicitly, noting that the quarter seizing has no riding turns.

The reason for two seizings rather than one is load distribution. The throat seizing carries the primary load — it is holding the eye closed against the tension trying to straighten the shroud. But a single seizing, however well applied, creates a stress concentration at its edges. The rope bends sharply at the boundaries of the seizing, and under cyclic loading this bend point fatigues faster than the straight rope above and below it. The quarter seizing spreads the transition — it takes some of the load from the throat seizing, and the bending now occurs gradually across the combined length of both seizings rather than abruptly at the edges of one.

The size Bushell specifies for the throat seizing on lower rigging: two-inch circumference seizing line, five fathoms length for the turns. The quarter seizing: one and a half inch, three and a half fathoms. The throat seizing is larger because it carries more of the load. The quarter seizing is smaller because its function is partly to distribute stress rather than primarily to carry tension. These proportions are not arbitrary — they are the result of working out, over many years of rigged vessels, what held and what did not.

The racking seizing in practice

The throat and quarter seizings on a shroud eye are round and flat respectively. The racking seizing appears where the load geometry is different — specifically where two parts of a rope are pulled in directions that would slide them past one another rather than simply apart.

The most common application is in the collar of a stay, where the two legs of the collar are seized together to prevent them from sliding relative to one another under the tension of the stay. A flat or round seizing applied here would hold the legs together but would not resist the tendency of the longer leg to creep relative to the shorter one under sustained uneven loading. A racking seizing, with its figure-eight crossing turns between the legs, grips each independently and resists the relative movement directly.

Bushell specifies racking seizings for the stay collars and for the heart seizings where a heart — the pear-shaped wooden fitting that replaces a deadeye in certain stay arrangements — is seized into the stay. In both cases the load on the seizing includes a significant shear component that parallel turns would resist less effectively.

Making a racking seizing takes more care than a flat seizing. The figure-eight path between the two rope parts must be maintained consistently — crossing on the front, round the back of one part, crossing back, round the back of the other, and so on. The turns must be kept under consistent tension throughout, because a racking seizing where some turns are tight and some slack has the tight turns doing all the work and the slack turns providing the appearance of strength without contributing to it. This is the same consistency problem that appears in serving, and the consequence of getting it wrong is the same — a fitting that looks adequate and is not.

I found racking seizings harder to make evenly than flat or round seizings, partly because the figure-eight path is less intuitive to maintain under tension and partly because it is harder to see from the outside whether the turns are evenly tensioned. The tell is in the gap between the two rope parts: a well-applied racking seizing shows even spacing of the crossing turns in the gap, each crossing sitting at a consistent angle. Uneven tension shows as irregular crossing angles, wider in some places than others.

Materials and finishing

The same material logic that applies to whippings applies to seizings. Tarred marline on tarred rope. Waxed twine on rope that has not been tarred. The chemical compatibility between seizing material and rope treatment matters for the same reasons — a seizing in a different material from the rope will move independently through wet-dry cycles rather than settling into the rope surface and becoming continuous with it.

The finishing of a seizing — the frapping turns and the final securing of the end — varies by type and by the load conditions. For flat and round seizings, Bushell passes the end of the seizing line between the two rope parts and winds several frapping turns around the parallel turns of the seizing, at right angles to them, pulling the parallel turns together and tightening them against one another. The frapping turns are then finished with a square knot or a half hitch. The frapping is what distinguishes a proper seizing from a simple binding — without frapping turns, the parallel turns can spread under load, reducing the clamping force they exert on the rope parts.

For racking seizings the frapping is applied differently, crossing between the two rope parts in the same figure-eight path as the seizing turns themselves, rather than perpendicular to them. The frapping in a racking seizing tightens the crossing turns rather than the parallel turns, which is the correct action for the geometry.

Inspection and renewal

A seizing that is working correctly is under continuous load and continuous exposure to the same conditions as the rope it is on. The same failure mechanisms — bacterial decay, salt crystallisation, internal abrasion — affect the seizing line as they affect the rope. A seizing that is degrading shows the same indicators: grey and dry surface where treatment has depleted, softness in the turns when compressed, visible fibre deterioration when individual turns are examined closely.

Seizings on standing rigging should be inspected when the rigging is inspected — at least at the start of each season, and whenever the rigging is removed for treatment or repair. The throat seizing on a shroud eye is the most load-bearing element of the whole assembly after the rope itself, and it deserves the same attention as the rope it is holding.

Renewing a seizing is not complicated, but the new seizing must be applied to rope that has been properly treated and is in good condition. Applying a new seizing to a degraded rope eye gives you a sound seizing on an unsound structure, which is a false security. The inspection of the rope beneath comes first, and the seizing renewal comes after.

One thing I have not yet worked out to my satisfaction: how to inspect the rope within the seizing without removing the seizing. The seizing conceals the rope surface beneath its turns — the most highly stressed section of the whole eye, the tight bend at the throat — and that surface is invisible without cutting the seizing away. Bushell does not address this directly. The implication of his retreatment schedules is that seizings are renewed regularly enough that the inspection happens at renewal, but this assumes a maintenance discipline that is not always realistic. For now I renew seizings at the start of each season regardless of visible condition on the working rigging, and accept that the cost of the seizing line and the hour of work is cheaper than the uncertainty of not knowing what is underneath.

What this is connected to

Seizings sit at an intersection of several threads in this series. The material choices connect to the dressings and treatments post — tarred marline is part of the same treatment system as the rope it binds. The load geometry connects to the grommets and strops post — a grommet strop seized into place uses the same seizing logic as a shroud eye, at a smaller scale. The inspection question connects directly to inspecting and retiring rope — the seizing is both a structural element that needs inspection and an obstacle to inspecting what is beneath it.

The worming, parcelling and serving post is where the mechanical protection system for the rope body lives. The seizing is its complement at the eye — the mechanical fitting that holds the eye geometry together while the service protects the rope surface. Neither is sufficient without the other, and Bushell, who understood the whole system as a system, applies both as a matter of course throughout the rigging specifications.

That integration — each element of the traditional standing rigging system performing a distinct function that the others depend on — is what I keep finding as I work through these sources. It was not over-engineering. It was a system developed to keep rope in service in the sea, under load, for as long as possible. The specific conditions that produced it have changed. The mechanisms that the system addresses have not.

Sources: Charles Bushell, The Rigger's Guide and Seaman's Assistant (Griffin & Co., 1874). Hervey Garrett Smith, The Marlinspike Sailor (International Marine, 1971). H.A. McKenna, J.W.S. Hearle and N. O'Hear, Handbook of Fibre Rope Technology (Woodhead Publishing, 2004).

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