• Ovals are very popular because their symmetry makes them good for many purposes.
• D carabiners also offer a good general-purpose shape and are stronger than ovals because more of the load is transferred to the long axis and away from the gate, the typical point of failure.
• Offset D's have the strength advantage of standard D's, but the gate on an offset D opens wider, making them easier to clip in awkward situations.
• Bent-gate carabiners are a specialty design most commonly used on difficult routes where it's important to quickly clip and unclip the carabiners from the feel of the gates alone. Bent-gate carabiners should always be used with a runner so that they are free to rotate.
• Locking carabiners, with a sleeve that screws over one end of the gate to prevent accidental opening, give a wider margin of safety for rappelling, belaying, or clipping into anchors. Some locking carabiners even have a spring that automatically positions the sleeve whenever the gate is closed. You must not forget to lock these carabiners, but you must always unlock them as well, which can be a nuisance.
• Pear-shaped locking carabiners are much larger at the gate-opening end than at the hinge end and are ideal for belaying with the Munter hitch. They are also a good choice for your seat-harness carabiner. The extra cost and weight are more than justified by the increased ease of loading and managing all the ropes, knots, cords, runners, and such that accumulate there.

Some carabiners are made from bars with cross-sections that are oval, T-shaped, or cross-shaped-as opposed to round-in order to save weight. Be aware that the T-shaped and cross-shaped material will greatly increase friction if they are used in contact with a running rope.

1. Always make sure the force on a carabiner falls on the long axis, and be especially careful that the gate does not receive the load.
2. Check the carabiner gates occasionally. A gate should open easily, even when the carabiner is loaded, and the gate should have good side-to-side rigidity when open.
3. Clean a dirty gate by applying a solvent or lubricant to the hinge (the lightest-weight oil, citrus solvent, or products such as WD40), working the hinge until it operates smoothly again, and then dipping the carabiner in boiling water for about 20 seconds to remove the cleaning agent.
4. Remember that a carabiner that has fallen off a cliff onto a hard surface has probably suffered hairline fractures and should be retired. Resist using such a "treasure" found at the base of a climb. In fact, you should resist using any critical climbing equipment if you don't know its history. Ropes, harnesses, runners, carabiners, protection pieces, and belay devices are all vital links in your chain of protection. Secondhand equipment, whether found or passed along without an account of its use, increases the possibility of a weak link in the chain you depend on for safe climbing.