Among common carabiner styles, which is the weakest?

• A. D-shaped
• B. Locking
• C. Non-locking
• D. Oval

Answer: (D)

The main idea here is how carabiner shape affects how the load is distributed across the metal. When a carabiner is loaded along its long axis, the way the load travels through the body matters: a shape that distributes that load evenly across a broad, rounded cross-section tends to be stronger, while a shape with sharper corners or a thinner spine concentrates stress in smaller areas.

A D-shaped carabiner concentrates more of the load along its spine and at the curve near the gate, which creates stress concentrations under major-axis loading. That makes it weaker in this loading direction compared to the oval style, which provides a smoother, more uniform distribution of force. Locking versus non-locking affects safety by preventing accidental opening, but does not inherently change the basic strength of the shape itself. So, among common styles, the D-shaped design is the weakest.