Carabiners were introduced to climbing in 1911 by German climber Otto Herzog, following Hans Fiechtl’s development of pitons. Pitons are pegs made of steel, from very soft to very hard, studied to be hammered inside rock cracks to protect the leading climber from falling.

Carabiners (aka connectors) are built with ultra-light aluminium alloys and open via a side gate, which can be locked with either a thread or a mechanical locking system.

There are four main shapes of carabiners.

  • Oval and symmetrical. Sides are straight and equal in length, curves are gentle and equal. They distribute evenly the equipment attached to them, but have the enormous disadvantage sharing weight equally between the strong side and the gate side.
  • D-Shaped. They are asymmetric and shift the weight on the strong side.
  • Offset D-shaped. These are strongly asymmetric, have a curve on the strong side and allow wider opening of the gate.
  • HMS carabiners are asymmetric and have a wide and gentle curve above the gate. They were developed to facilitate the use of the Italian hitch.

European standards (EN12275) recognize and regulate a total of seven types of carabiners[1]. To be certified they have to withstand three resistance tests: a longitudinal pulling of at least 20kN (with the gate closed), a latitudinal pulling of about half that force and a final longitudinal test with the gate opened. Any carabiner loses two-thirds of its resistance when the gate is open and so the test requires carabiners to withstand a force of 7kN only when the gate is open.

Although European Standards and the UIAA establish a minimum force carabiners should withstand, manufacturers can create carabiners much stronger than that. Each carabiner you buy must have a CE mark and state the kN it is guaranteed to withstand on each of the three tests. These are the values imposed by EN12275

Vertical Resistane
Open Gate Resistance
Horizontal Resistance
A Special piton 20 kN
B Base carabiner 20 kN 7 kN 7 kN
D Directional 20 kN 7 kN
H HMS 20 kN 6 kN 7 kN
K Via ferrata 25 kN 7 kN
Q Maillon Rapide 25 kN 7 kN
X Oval 18 kN 5 kN 7 kN


In regards to the locking system, you can choose between four different systems: screw-gate, automatic-gate, twist-lock and auto-lock. The most used locking system in sport climbing still is the old and nice wire-gate, appreciated for its simplicity and safety. Many climbers like the twist-lock system and only a little percentage use regularly the automatic gate and the auto-lock.

A part from shapes and locking system, when buying a new carabiners we advise to choose Keylock carabiners, without that annoying hook to lock the gate. Not having that gripping hook will spare you from swearing when trying to get it out of a small anchoring point.

Look at the image on the side and you can immediately see where the problem is…

[1]The other three types of carabiners are: the ones specific for Via Ferrata, those without locking gate and the Special Piton carabiner used in anchoring points.