A Guide to Carabiners

A carabiner hook (or karabiner) is a loop of metal with a spring-loaded gate that opens and shuts. The name 'karabiner-hook' comes from the people who made them popular - European soldiers who carried the first 'carbine' rifles. Uses are various and allow workers and climbers to join virtually every piece of equipment, allowing us to move in the vertical world safely, quickly and efficiently. 

Today, you can find of dozens of designs, shapes and models of carabiners that all serve particular purposes. Below is a simple guide to helping you choose the right carabiner for your purpose: 

Shape: 

• Karabiner or Hook? As a guide, if it is shaped like a single loop then it's a karabiner. The gate-locking mechanism is also fitted on the gate, not across the entire connector. A 'hook' uses a seperate eye to keep one end permanently or semi-permanently attached, and usually the gate-opening mechanism is on the back spine of the connector.
• Oval Shaped: The original shape of a carabiner. It allows for easy opening, and it also prevents shifting when loaded. Due to its shape it is not always able to carry as much as some of the larger carabiners, but the smooth bottom and top is useful for hanging wide-spaced equipment without 'crowding' the parts together.
• D-Shaped: The D-shape is larger than the Oval and has a wider gate opening. This shape is the “standard” carabiner and the most commonly used. It is generally lighter in weight than the oval with increased strength, but the narrow bottom will pull multiple pieces of equipment together. Best used with single attachments or narrow pieces.
• Asymmetrical D-Shape: The asymmetrical D-shaped carabiner is the most popular design because it is the lightest shape, strongest design and has a much larger gate opening than regular Ds. 
• Pear Shape: The pear shape has an extra-large gate opening. Great for anchoring ropes and other gear together though they can be more difficult to operate than the Oval or D Shaped.

Locking Mechanisms:

• Screwgate Locking: The screw needs to be manually turned to open and shut the gate, which some people prefer (rather than relying on an automatic spring mechanism).
• Maillon: A maillon (or quick-link) has no gate, the screw-lock simply opens by turning. Due to that, it is usually closed with a spanner to ensure that it stays closed for semi-permanent connections.
• Self-Locking / Auto-lock: automatically close when the gate is released and are available in:
• double action (twist-open), and
• triple action (slide-twist-open). New regulations spreading in parts of the industry are now requiring a carabiner with a three-action locking mechanism on the gates for added safety.
• Specialist Locking: These specialist carabiners include Ball-Lock (made by Petzl) with a small ball you push in to open the gate or Pin-lock where a special pin-tool is used to unlock the gate.
• Non-locking spring gate: These are not suitable for life-safety items such as attaching ropes, but are popular for temporary positioning of items which need quick-release (such as seats, accessories, tools, and quickdraws).

Examples of popular models: 

Petzl WILLIAM Aluminium Karabiner (2016): The updated WILLIAM asymmetrical large capacity aluminium karabiner has a pear shape that is practical for easily connecting multiple items. Its fluid interior design and Keylock™ system facilitate manipulations. The WILLIAM karabiner is available in three locking systems: SCREW-LOCK manual system or TRIACT-LOCK and BALL-LOCK automatic systems.  

Kong 411 XL D Screwgate Karabiner: The Kong 411 XL D Screwgate Carbon Steel Karabiner with screw sleeve. The X-Large is designed to offer a wide gate opening and a high tensile strength. The particular D shape prevents the rotation of the karabiner and allows to distribute the load along the major axis. Equipped with Key Lock system that prevents any snagging on the rope and in the bolts. Fitted with screw sleeve, easy to open even wearing gloves. 

Skylotec DOUBLE TRI Tri Lock Karabiner: The new DOUBLE TRI, is the new generation of HMS karabiner with 180 ° technology and smooth triple-locking mechanism for maximum safety - push up, turn and open. With the new karabiner series DOUBLE, SKYOLTEC has now an answer for all those who work and climb left-handed or use both hands. With the innovative design (180° spring rotation), the sleeve that closes the gate can rotate in both directions.

ISC Small Iron Wizard Screw Gate Karabiner: This small ISC Iron Wizard steel carabiner features an awesome 70kN breaking strength and four gate configurations. The offset gate swings open to the side to allow for maximum clearance.