Splicing 101

Rope splicing is an old skill passed down to arborists from the days of tall ships on the high seas. Like knots, splices were a rite of passage and often served to separate the old salt from the landlubber. Today, splices permeate the arborist marketplace. A rope’s ability to be spliced and in what configuration are often major factors for deciding which rope to climb or rig on.

Ease of splice, compactness and loss of overall line length are but a few considerations. Splices have some distinct advantages. Their ability to retain 90 percent or more of the rope’s ultimate strength, their ease of use and trimness, or lack of clutter, at a connecting point, whether it be log or harness, all make splices appealing to the modern arborist.

However, with the plethora of materials, constructions and braid choices, splices and splicing has become a bit of necromancy. The uninformed may choose or use splices that are not appropriate either for the application and/or material. Furthermore, as Clifford Warren Ashley said in his tome “The Ashley Book of Knots:” “A knot is never nearly right; it is either exactly right or it is hopelessly wrong, one or the other; there is nothing in between.” The same holds true for splices, but unlike knots, splices do not reveal their flaws as readily. However, a proper splice has an external form that allows for the user to determine its “rightness.” It is this inspection process we will explore in its most basic form.

By providing you with general guidelines on splice inspection and use we will empower good choices, with a firm grounding in function. While space limits the amount we can cover, and no article should be considered the ultimate resource on all things splicing, we can get a good start. To further narrow our scope, we will specifically discuss the most prevalent splice in arboricultural operations, the eye splice as formed in double braids, 16 and 24-strand and hollow braid constructions.

Photo: Tony Tresselt

Manufacturer’s recommendations

Half of the parallel lock sticking can be seen at the red arrow. The other half goes in from the opposite direction, holding the horizontal wraps in place. How this is accomplished is often the trademark of individual splicers.

As stated earlier, the sheer volume of materials and constructions in modern arborist lines is astounding compared to just a decade ago. There are few, if any, single sources of information on every rope of every material. The splicer must refer to the individual manufacturer’s specific recommendations for each rope. These are the “rules of engagement” when it comes to splicing and application. While we will review some general specifications to look for in splices, the manufacturer’s guidelines should be followed exactly for every splice. A firm grasp of these for the ropes you routinely employ will go a long way to determining the quality and functionality of a splice or spliced product.

Pieces and parts

Like knots, splices have specific parts that make up their whole. Unlike knots, there is not much familiarity in these terms. For the purpose of this article I will lay out a basic nomenclature so we can clearly discuss splices. This is not a researched terminology, just terms I have found most commonly used and most descriptive.

Eye — The eye of the splice is the bite or termination formed. It is the reason for eye splices and the interface between rope, splice and connecting link.

Bury — The bury of the splice is the amount of cordage fed back into the rope to create friction to hold the splice together. The amount of bury is splice, cord and material dependent. Remember that bury length is determined more by fiber type than construction. While Tenex and Amsteel (both Sampson rope products) have common constructions, the bury distance is hugely different.

Taper — This is the section of the bury where individual strands are removed to allow for a snug bury, as well as to reduce stress risers of possible weaknesses in the finished splice.

Throat — The throat of the splice is the area of the bury that was not tapered. It lies immediately below the eye. In a double braid splice, the throat also contains the crossover.

Crossover — The crossover is the section of a double-braid splice where the core enters the cover and the cover enters the core. This is the thickest section of the bury, and the one most likely to have discrepancies if not spliced properly. It also refers to the point in some hollow braid spliced products where the ends of individual tapers may cross. In either case, the crossover should be smooth and nearly undetectable.

Lock stitching — This is the added-on stitching after the splice is run home and firmed up that is applied along the bury of the splice. It comes in as many shapes and forms as there are splicers. It is often the trademark of a specific technician. It keeps the eye from elongating under low load. It also prevents a splice from being teased loose when not under load. The greatest load provides greatest friction, thus a splice is most secure when loaded. Unloaded splices with fibers relaxed can snag on a branch and possibly tease out. Lock stitching is vital on all arborist splices.

Manufacturer’s tag — This is a numbered label attached to some premanufactured splices and all commercial slings. Depending on the application, it may be required by regulation. It may or may not give load ratings for specific configurations, a serial number and date of manufacture.

Here the end pre-trim of an invisible lock stitch can be seen, as well as the smooth transition of the top of the throat entering the rope at the base of the eye. Photo: Tony Tresselt


When looking to purchase a splice from a vendor, look for the manufacturer’s tag or label. While simply slapping a marked piece of paper held in place by a shrink tube is no guarantee of quality, it does give the end user some benefits. The tag should contain a serial number and a name of either the splicer or the company he works for. This is not a law, but a good indication of an in-place quality control system, knowledgeable, trained splicers and a fallback should there be problems with the splice during use.

This is not to say that high-quality splices are not available from talented splicers in an “off-market” situation. I am only recommending that if you purchase a splice and do not know who spliced it and trust them implicitly, then a tag can go along way to assuring you are receiving a quality, tested product.


Part of the necromancy of splicing is the ubiquitous fid length. For all its mystery, it can be equated down to a simple formula:

Long fid = 21 rope diameters
Fid = 14 rope diameters
Short fid = 7 rope diameters

Notice the multiples of 7 for easier recall. Also, this is a general rule. Please refer to the specs for a particular rope and its manufacturer for exact numbers.

Here the core 9white) and the sheath (green) can be seen entwined before a class 1 double braid splice is run home. Photo: Tony Tresselt


With a common terminology, we can now delve into what to look for. First and foremost, you need a firm understanding of what material you are inspecting and what its application will be. The myriad of line choices available today is incredible. The types of applications on just one tree job can be staggering. The days of one line fits it all are gone. Choose your lines wisely and follow the manufacturer’s recommendations. Some lines, due to construction and materials, cannot be spliced. As a consumer, you will not be able to tell unless you know what line you are looking at and its limits.

Some splices require very long buries, thus making the bury of the splice stiff away from the working end of the line for some distance. This may make a choker hitch as a termination difficult on small diameter anchors.

The length of throat and, hence, the length of the bury is a measurement determined by the rope manufacturer. It is measured in fids and should not be altered. Knowing the fid length and how to determine it on the splice itself leads us to our next point. A last warning on fids; this is also the name of a splicing tool that is sized to measure as well as bury. If you are using an actual fid as a length measurement, make sure it is scaled 1:1 for the rope size. Some larger fids are scaled down to make them physically manageable.

Bury length

Once you determine the material, run your hand along the splice and feel the throat, taper and bury. The bury should smoothly taper off as you move your hand away from the eye. The length of the bury should match the manufacturer’s specs. On excellent splices, the end of the bury will be difficult to determine. This alone is sign of a high-quality splice. The throat should be smooth without frayed strands, bumps or other signs the crossover is malformed or distorted. A high-quality splice, like a well-formed knot, is smooth and nice to look at in its symmetry and form. Never accept mediocrity. Sloppy splices are compromised splices and should not be trusted.

Half of the parallel lock stitching can be seen at the red arrow. The other half goes in from the opposite direction, holding the horizontal wraps in place. How this is accomplished is often the trademark of individual splicers. Photo: Tony Tresselt

Lock stitching

Finally look for the lock stitch. It should be high up on the splice as close to the crossover as the stiffness of material will allow. It should be neat and tight, but not distorting the splice. The stitching should engage the rope in multiple dimensions along its length.

There are some forms of lock stitching that are not readily seen. Approach these as you would a manufacturer’s tag. If you know the splicer and are sure that a lock stitch has been applied properly, then use the splice. Hidden lock stitches can also be checked by trying to pry the bury back out of the rope or elongating the eye. If this can be done by hand, the splice is suspect. If you do not know who formed the splice, then I would recommend you insist on visible lock stitching.


There you have it. A basic splice inspection system combined with basic terminology. As with all life support system elements from knots to harnesses, thorough understanding of limits and applications is necessary to assure safety and function. Splices are no different, and together we have laid out a good basis for splice inspection.

We have by necessity only covered the basics. I encourage you to research and increase you splice knowledge. This topic is also the subject of a short audio podcast.

If it seems we have ignored the venerable three-strand splice, you would be correct. Unlike braided ropes, twisted ropes do not conceal splicing flaws as readily. Hence, they are slightly easier to inspect. However, three-strand ropes have their own peculiarities and still serve many arborists and as such deserve an article of their own.

Remember to regularly inspect all your equipment. Err on the side of caution, and when purchasing any cordage product including splices, a knowledgeable consumer is a safe consumer.

Editor’s note: This story was originally published in May 2011 and has been updated.


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