Classification Terminology
Used on this Site


ovalovalclassic symmetrical ovalA classic shape easily formed with simple tooling. Still in use because the symmetrical shape reduces shifting under load.
DDtrapezoid D shape with parallel gate and spineAs with the Oval, the gate and spine are parallel, but D shaped carabiners shift the load away from the gate, permitting lighter carabiners for the same strength rating (or stronger carabiners for the same weight).
asymmetric Dasymmetric Da D-shaped carabiner with one end larger than the otherBy shrinking the hinge end the D shape is lightened further with little impact on usability. Conversely, for the same weight the gate opening is larger than a symmetrical D shaped carabiner.
swept spineswept spinespine forms a bend arcing away from the gate sideSwept shape is easier to grip than a straight spine, but can reduce gate opening or increase weight depending on design.
Omega Pacific JC
bent spinebent spineasymmetric D with a single bend in the spineCreates a larger gate opening and basket than an asymmetric D. Can be easier to clip one-handed when used on a rock climbing quickdraw or similar.
Example: Black Diamond Dynotron
S-spineS-spinetwo reversing bends in the spine, forming an S-shapeSimilar features to a basic bent spine, but the s shape can be easier to hold, especially for large carabiners such as the:
Petzl Vertigo.
HMSHMStriangular, or slightly swept-spine asymmetric D shaped carabiner with large enough basket for a Munter hitchA large basket permits easy use with a Munter Hitch (Halbmastwurfsicherung in German)
Petzl Attache
hourglasshourglass8-shaped carabiner with narrow waistAn evolution of the HMS carabiner with a restricted small end of the carabiner to encourage proper loading of the carabiner. Often present with an additional anti-crossloading feature.
Example: Black Diamond Gridlock
other shape, modeled after the Grivel Vlad carabiner with integrated rigging plateother-for everything else


Cross-sectional profile of the carabiner.

In general, I try to categorize carabiners using the profile along the spine, rope running surface or the profile which best represents the manufacturing method.

The Omega Pacific Jake typifies the T-Beam profile, and the BD Quicksilver2 uses a similar profile with softened edges. I have classified the Petzl Spirit v1 as a hollow-trapezoid shape, but the design splits the differences between T-Beam and Trap profiles.

The Petzl Spirit v2 clearly uses an I-beam (H-Beam) profile, but the BD LightForge softens those edges significantly, pushing it into a baseball-bat cross-section in places and I-beam in others. And I've classified the BD Dynotron v1 as hourglass, but it is essentially a trapezoid shape with a minor groove. The hemispherical grooves are technically more than 45 deg near the surface and could be considered a crude I-Beam

Styles can be murky to tease apart, as some carabiners have a blend of profiles, with different cross-sections along the carabiner body. Rarely do modern carabiners use a consistent profile along the entire carabiner body, thanks to improvements in computer design, materials engineering and use of a hot-forge process.

As an example, let's look at the Grivel Clepsydra S:

  • Designed as a belay carabiner, the basket uses a round profile for smooth and durable rope running.
  • Near the nose, the round profile of the basket has been smashed into a trapezoid profile.
  • The anti-crossload gate hinge is anchored in a T-beam profile. Mirrored from the typical orientation, the stem of the 'T' faces the interior of the carabiner and permits the anti-crossload gate to swing open.
  • The small (hinge or runner) end of the carabiner forms a sharp baseball-bat profile, almost a relaxed I-beam.
  • Most of the rest of the body is an hourglass profile, blending a bat profile into a T profile into a round profile.

For the purposes of classification, I have the Clepsydra listed as an hourglass profile, but I would not fault anyone who would think otherwise. Perhaps someday, I'll evaluate the basket, spine and runner/hinge end of a carabiner separate from one another.

a circleroundformed from round rod stock
ovalflatformed from round rod stock, flattened into an oval cross-section
trapezoidtrapezoidsimilar to flat forming, but tapers towards the outside/spine of the carabiner
hollow trapezoidhollow-traptrapezoid with the concave sides
diamonddiamondtapers from the thick center to the thin edges. A double-sided trapezoid/hollow trapezoid or reverse-hourglass.
T-BeamT-beamwide at the interior of the carabiner with a narrow spine
hourglasshourglasshourglass or figure 8 cross-section, thicker at either end of the profile and usually not symmetric - some carabiners have both an I-beam and hollow-trapezoid profile
applecoreapplecoreCurved section does not exceed 45 degrees without the bulbous ends as with hourglass profile. Almost a hollow flat profile.
I-beamI-Beamexaggerated hourglass or applecore, with the reinforcing rib forming angles greater than 45 deg towards the interior of the profile, often closer to 90 deg
baseballbatbaseball-bathybrid between an hourglass and I-beam
webbed I-beamWebbed
Like an I-beam, but has distinct areas where the center of the I is thinner and thicker.

Rivet Style

Most gates are attached to the carabiner body with some sort of rivet or pin. The ends of the wire in a wiregate are finished in a similar manner.

A rivet is a pin with flared ends, that flaring can take different shapes which affects how the carabiner handles. One end is usually pre-formed, and the other end formed once the carabiner has assembled. Most auto-locking carabiners use a (pre-formed) stud on one end of the hinge rivet to index the locking sleeve. In this case, this term describes the finished end.

Admittedly, this term is somewhat subjective as styles represent a blend of both manufacturing methods and design choices, and some styles are very similar. I consider an edge sharp if I can scrape off part of my fingernail against the rivet edge. In my experience, edges this sharp will pick and catch on rope fibers. This does get murky on well-used carabiners with worn rivet edges.

domed rivetdomedsmooth-edged domed shaped rivet
flat spun rivetflat spunsharp-edged rivet spun almost flush with the gate
flat & dimpled rivetflat-dimpledsharped-edged with central dimple
flush rivetflushriveted head (not a pin) driven flush or slightly recessed - no sharp edges as found in flat-spun rivets. May be difficult to determine with worn carabiners.
recessed pinpin: recessedpin driven beyond flush of the gate, no head
proud pin sticks above the surfacepin: proudpin left proud of the gate surface
domed + flat spuncombination of styles

Nose Guard

In conjunction with the gate spring tension, a guard helps protect an unlocked carabiner gate from opening if dragged (flat) across a (rock) surface.

This feature may sometimes be referred to as a shrouded or hooded nose, especially with wiregate carabiners.

none none no guarding, wire fully exposed
minimal minimal guard does not extend the full length of the nose, or beyond the inner edge of the gate
semi guarded semi guarding which extends the full length of the nose, but not beyond the width of the gate wire
full nose guard full guarding which extends the full length of the nose AND the width of the gate wire

Gate Shielding

If loaded along the minor axis (crossloaded), the rear of the gate can rapidly shred a rope.

Older carabiners tended to have a large square cut-out, which clears debris and ice relatively easily, but may damage the rope under a heavy crossload. More modern designs have a smoother surface on the rear of the gate to prevent damage. This feature is sometimes referred to as a shielded or shrouded gate, but I have chosen to stick with a gate shield to avoid confusion with a nose shroud/hood/guard.

none none gate cutout fully exposes the notch and nose of the carabiner. Bottom of the cut may be square (older style) or rounded.
semi semi the rear cutout on the gate does not extend below the nose of the carabiner, but does leave the pin or notch exposed slightly
full full a fully guarded, smooth rear gate surface extending beyond the pin (if present). May have slight relief cut at the top, which provides a bit more gate clearance when fully open
relieved relieved relief hole in the rear of the gate aid clearing of ice and debris so the gate will seat properly or be less likely to freeze closed


On the individual carabiner pages, I have tried to describe the markings present on the carabiner.

In some cases I have included a small generic version of the icon on the carabiner, but for greatest accuracy refer to the photos for the exact style of icon used on the particular carabiner.

A guide to understanding my marking descriptions:

Marking EntryMeaningExamples
<Marking Type>:My best guess at how the mark was formed.

Forged/Stamped can be difficult to discern for recessed letters. Some carabiners were stamped (or rollmarked) for the ratings/logo and stamped separately for batch/date/lot markings.
| Divides markings between those found on different surfaces of the carabiner.side [gate‑right]
side [gate‑left]
(ratings)The set of strength ratings marks including the orientation icons.23kN
(read)One of the many icons encouraging the user to read the technical notice.
(factory icon)A silhouette of a factory including a stack and iconic (literally) saw-toothed roof.

Typically, indicates the batch, lot or date code for tracking and quality assurance.
(x-circle)A letter in a circle indicating the class of carabiner, as described in UIAA or EN ratings
(lock icon)Icon of a (locked) lock. Typically shows the direction needed to lock, or is revealed when carabiner is correctly locked.
(crossbones)Icon of a skull and crossbones. Generally indicates danger, need for caution, or possibly deadly configuration.