Carabiners are links that join equipment and rope into a functioning system. Used properly, they are strong, versatile items. Carabiners are strongest along the long axis and any sideways loading (across the gate) can severely reduce the strength to the point of gate failure. We do not recommend the use of brake bars on carabiners. This has been known to cause gate failure in carabiners. D‑shaped carabiners are stronger than ovals. The D shape directs a larger share of the load to the longer side opposite the gate. Carabiners are made of aluminum or steel. Steel are the strongest and they hold up under wear. People using carabiners for sports, such as climbing and caving, usually prefer aluminum for its light weight. Those involved with rescue and industry tend to prefer steel for its higher strength. Carabiners must be closed before applying a load, as they lose strength when in the open position. Loading an open carabiner can have catastrophic effects due to failure of the frame. All carabiners listed in this catalog have spring loaded gates which automatically close once they are released. Whenever the gate stops functioning, it must be replaced.
Non‑locking carabiners have the advantage of ease of operation and should only be used in situations where they can not be accidentally opened, such as by pressing against ropes, cliffs or buildings, etc.
CAUTION: If non-locking carabiners are used to support a critical load, two must be used. The carabiners are oriented so that the gates are opposite and opposed to each other. It is unlikely that both gates would open at the same time, increasing the safety of the system. Many people in rescue and industry prefer locking carabiners. The locking nut should be turned only to finger tightness before applying a load. If it is locked tighter, or tightened under load, it may be very difficult to unlock by hand. To correct this, reapply a load to the uncooperative carabiner and loosen the nut under load. Make sure you are in a safe location before attempting this, as the carabiner may be the only item connecting you to safety.
When using a sit harness where a sideways (or three-way) loading will occur, the user must use a triangular screw link or extra-large carabiner as cross-loading can cause failure. Screw links take more time to operate. Be careful when purchasing screw links. Many hardware stores sell screw links which are intended for repairing chains. These are not good choices in a critical situation. All of the M.R. screw links listed in this catalog are adequate to accommodate ropes up to 5/8”(16mm) in size. M.R. makes three styles: an oval which is used in the same manner as a locking carabiner; a triangular; and a semi‑circular model. The last two are excellent where three‑way loading will occur, such as in sit harnesses. Keep the threads of all locking nuts clean and free of grit. Carabiners get weak from repeated stress. When they show wear or have been exposed to a fall factor of greater than one, they must be retired from critical service. Check the spring loaded gate and pins often. If the spring fails or is sluggish, or if the pins show signs of corrosion or wear, it is time to retire it. NEVER hang your life on anything which is damaged or badly worn.