Rope Grommets and Strops — Making and Using Traditional Rope Fittings

Collection: Regenerative Materials | Series: Natural Ropes |

Subject: What grommets and strops are for, how to make them, and what the old sources reveal about load distribution that most modern accounts miss

A fitting that makes itself

A grommet is a single-strand rope ring. Nothing is joined to make it — no separate pieces spliced together, no knot, no fastening. A single strand unlaid from a rope, worked around itself three times until the original lay is reproduced in ring form, the ends tucked back into the structure and disappearing into it. When it is done correctly it looks as though it grew rather than was made. When it is done incorrectly, which takes considerably more practice to avoid than the descriptions suggest, one side is loose and the other tight and the whole thing wants to twist rather than sit flat.

I came to grommets through blocks, and to blocks through the realisation that wooden blocks with rope strops are not simply a heritage curiosity. They are a genuinely different mechanical object from a metal block with a metal becket, and the differences matter for how loads are distributed through a rig. Smith covers grommet-making in The Marlinspike Sailor with his characteristic economy — the instructions are clear enough to follow and leave out enough detail that you discover the gaps through practice rather than preparation. Bushell's Rigger's Guide approaches the same subject from the professional rigger's side, with dimensions and proportions specified rather than implied, and it is the Bushell account that is most useful for understanding why a strop is made the way it is rather than simply how.

What a grommet is for

Before making one it is worth being clear about what it is for, because grommets serve several different functions and the making method is the same for all of them while the material, diameter, and finishing vary considerably.

As a strop for a wooden block, the grommet encircles the block shell and forms the loop by which the block is attached to a spar, a fitting, or another rope. The strop distributes the load of the block's working tension around its full circumference rather than concentrating it at a single attachment point. This is the central mechanical advantage of a rope strop over a metal becket — the load is spread across the contact area between rope and wood, and the wood is supported from all sides rather than hanging from a single bolt. The Handbook of Fibre Rope Technology notes that the strength reduction at a thimble or eye fitting depends critically on the bend radius and the contact geometry, and a well-fitted rope strop produces a more gradual load transfer than a metal becket can.

As a thimble strop, the grommet holds a metal thimble — the teardrop-shaped insert that prevents a rope loop from being abraded at its bearing point — in a fixed position where it can be seized into the standing part of a stay, shroud, or halyard. The grommet here is working as a precision fitting, not merely as a loop, and the dimensional accuracy matters more than in less exacting applications.

As a repair tool and temporary fitting — a ring to go over a spar end, a stop for a fitting that has worked loose, a temporary deadeye substitute while a proper repair is made — the grommet is valued for being makeable with nothing except rope and a marlinspike, in whatever diameter the available strand material allows, without any other hardware.

Making the grommet: what the sources say and what I found

Smith's method is the clearest starting description. Take a single strand from a length of rope — unlay one strand the full length you need to work with, which is approximately three and a half times the circumference of the finished grommet. Make a loop of one-third the strand length, laying the short end alongside the long end so they cross at one point. Then work the long end around the loop, following the lay of the original strand, filling in the spaces between the existing turns exactly as they were in the original rope. When the long end arrives back at the crossing point, tuck both ends into the body of the grommet to finish.

The instruction that sounds simple and is not: "following the lay of the original strand." What this means in practice is that the strand, as you work it around the ring, must maintain the same helical character it had in the rope — the fibres spiralling in the same direction, at the same angle, with the same tension. If the tension varies, the grommet will be uneven. If the direction varies, the structure will not reproduce the original lay and the ring will not hold its shape under load.

My first attempts were loose on one side and tight on the other, the classic beginner's result. The cause, I eventually understood, is that the strand has inherent spring — it wants to return to its straight form — and working around a ring requires consistently overcoming that spring with even hand tension throughout. A piece of dowel or a round spar the diameter of the intended grommet interior, used as a former, helps enormously. The strand is worked around the former rather than around itself in free space, and the former holds the geometry while you concentrate on maintaining even tension in the working strand.

The second thing the descriptions do not tell you clearly enough: the three passes around the ring must reproduce the exact spacing of the original rope lay. Too close together and the grommet is dense and stiff. Too far apart and there are gaps in the structure. The target is a ring that looks, in cross-section, like a small three-strand rope — which is what it is, formed in a circle.

Dimensions and proportions

Bushell gives specific proportions for block strops that I have not found clearly stated elsewhere. The circumference of the strop rope should be approximately one-third the circumference of the block shell. The length of rope required to make a grommet strop for a block is three times the round of the block plus three times the round of the thimble, plus three times the round of the rope itself to allow for splicing the grommet closed — Bushell gives this formula for several block sizes, and the pattern is consistent.

The diameter of the grommet's ring — the interior diameter, across the space enclosed by the rope — determines what it can fit around, and Bushell's specifications make clear that precision here matters for wooden blocks specifically. A strop that fits too loosely around the block shell will shift under load and concentrate strain at one point rather than distributing it. A strop that fits too tightly will deform the block shell under sustained load. The strop should fit firmly around the block's maximum diameter with no slack, but without compression.

This is the kind of dimensional reasoning that is absent from most modern accounts of traditional ropework, and it makes sense of why the professional rigger's approach — Bushell's approach — specifies dimensions rather than describing a technique. The technique produces a grommet. The dimensions determine whether it does its job.

Strops that are not grommets

Not all rope strops are grommets. A salvagee strop — Bushell spells it salvagee, Smith uses selvagee — is made by winding rope yarn or small-stuff repeatedly around two pegs set at the required diameter apart, then passing a binding of yarn around the whole bundle to hold it together. The result is a flat, soft, highly flexible strop that conforms to irregular surfaces better than a round grommet can, and that distributes load across many parallel yarns rather than across three strands. Bushell uses the salvagee strop for heavy purchase work — hooking into chains, around spars too large or too irregular for a grommet to fit cleanly.

The making method is simpler than a grommet but less intuitive to understand. The bundle of yarn, wound back and forth around two pegs, looks nothing like a rope strop until the binding is applied and the whole thing is pulled into a ring. The binding must be tight enough to hold the yarns in coherent relationship to one another without cutting into them. Too loose and the yarns spread under load. Too tight and they are damaged at the binding point.

Smith describes this briefly and usefully. Bushell provides it as a working tool in the rigging process — it appears as equipment for hauling, not as a decorative or historical item. That context tells you something about its value. These are working fittings that professional riggers made on demand from available materials. The skill was not in the artistry but in the reliability under load.

The preservation question

A grommet strop in working service is in the same conditions as the rope it is made from — wet, salt-cycled, under sustained load. The same failure mechanisms that destroy rope destroy strops. The geometry of a grommet, with its internal strand contacts under the compression of the strop's working tension, may actually accelerate internal abrasion relative to a free rope of the same construction — the contact pressure between the strands is continuously maintained by the load the strop is carrying.

Treating a grommet strop before use follows the same logic as treating rope. Immersion in warmed Stockholm tar for several hours, the strop dried properly before fitting, and the wood of the block shell also treated so that the two surfaces in contact — rope and wood — are both protected from moisture ingress at their interface. Whether the treatment penetrates uniformly into the tight internal geometry of a finished grommet is less certain than for a straight rope — the compression of the strop structure resists penetration in the same way that hard-laid rope does. Making the grommet slightly looser than the final fitting diameter, treating it, and then working it to final size over the fitted block may improve penetration relative to treating a grommet that is already under compression. I have done this with two strops so far and they have taken treatment more evenly than strops treated after fitting. The comparison is not controlled — too many other variables — and I hold it as an observation rather than a conclusion.

The serving question is whether grommet strops should be served over. Bushell serves the strop of a block over its full length as standard practice for larger blocks, and it is easy to see why — the contact between rope strop and wooden shell, particularly at the scoring (the groove cut into the shell to seat the strop), is a chafe point under every cycle of load. A served strop resists this abrasion at the contact points and protects the strop surface from salt and UV at all other points. For smaller blocks and light-duty strops, serving is probably more effort than the application warrants. For standing blocks on a working rig, it is the correct approach.

What the Handbook adds

The Handbook of Fibre Rope Technology covers thimbles, pin diameters, and the strength reduction at eye fittings in the kind of detail that is useful for understanding why the proportions matter. The key finding, stated in terms of the ratio of thimble diameter to rope diameter, is that bending rope around a small radius reduces its effective breaking strength substantially — a ratio below about five times the rope diameter produces a significant strength reduction, and below three times the reduction becomes severe.

This applies directly to grommet strops, because the grommet itself creates a bend at the point where it passes around the block shell, and the tightness of that bend is determined by the ratio of grommet diameter to block shell diameter. Bushell's proportion — strop rope circumference approximately one-third of block circumference — produces a grommet diameter relative to the rope diameter that sits within the acceptable range, which suggests the traditional proportion was developed empirically to avoid the strength reduction that too tight a bend produces. Whether the original riggers understood this in terms of bend radius ratios or simply observed that strops made to these proportions held while strops made tighter did not, I do not know. The outcome is the same either way.

A note on wooden blocks

Making blocks to fit the strops — or strops to fit existing blocks — is a subject adjacent to this post and properly part of the deadeyes and wooden blocks post later in this series. The connection is worth noting here because the strop and the block are a system rather than independent components, and the proportions of one are constrained by the proportions of the other. A strop made correctly for an incorrectly sized block is still an incorrectly sized assembly.

The shell diameter, the pin diameter, the sheave diameter, and the scoring depth are all interdependent. Bushell gives tables for these proportions at different block sizes, and they are worth taking seriously rather than improvising around. Wooden blocks fail at the pin, at the sheave, and at the strop — in that order of frequency in the sources I have read — and the failures at the strop are almost always at the bearing point where strop meets shell, which is where the bend radius and the surface protection both matter most.

I have made strops that failed at the shell bearing point after one season and strops that have held through three. The difference, as best I can reconstruct it, was not the grommet-making quality but the combination of shell fit, surface treatment at the contact point, and whether the strop was served there or not. The variables compound, and isolating any single one from the others in practice is difficult. It is the kind of problem that rewards patience and systematic variation rather than intuitive adjustment, and I have not yet been systematic enough about it to draw confident conclusions.

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

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