Triple Lock

A triple lock carabiner is a type of carabiner that features a locking mechanism with three steps to ensure the gate stays closed and secure. These are typically used for critical applications like climbing, rappelling, and caving where an accidental opening could be disastrous.
The three locking mechanisms typically involve:

Auto-lock: The gate itself has a spring-loaded mechanism that automatically closes the gate when it is pushed shut.
Twist Lock: A sleeve on the spine of the carabiner must be twisted to unlock the gate.
Keylock Nose: The nose of the carabiner is designed to prevent snagging on ropes or webbing.

Not all triple-lock carabiners will have exactly these features, but they will all have some kind of three-step locking mechanism to maximize safety. These carabiner are typically more bulky and heavier than screw-gate carabiners, but the added security makes them ideal for high-risk situations.