HMS or pear-shaped carabiners provide a larger basket for Munter hitches and belay stations; D shapes suit many device-to-harness connections. Petzl notes pear shapes can rotate more readily while D shapes tend to stay positioned. Follow the exact device and carabiner instructions.
A belay carabiner must match the device, load direction and use instructions. Shape and gate mechanism are separate choices.
Compare common shapes
| Shape | Maker guidance | Fit check |
|---|---|---|
| HMS or pear | A large basket suits belay stations and a Munter hitch | Confirm the device sits in the intended position and cannot turn into a cross-loaded orientation |
| D | A common shape for attaching a device to a harness | Check the actual device manual and frame orientation |
| Oval | Symmetric shape used with some pulleys and devices | Use only for the intended connection |
Petzl’s carabiner-shape guide says pear shapes may rotate more readily and D shapes tend to stay positioned better. It also emphasizes that shape affects loading and handling.
Choose a locking system
Petzl describes screw-lock systems as manually locked and notes their handling can suit harsh environments where mud or ice may affect automatic systems. Automatic locks can suit frequent use, but each requires its own opening and locking checks. Read the exact model instructions and verify the gate is locked.
Check standards and device compatibility
The UIAA lists UIAA 121 for connectors. Petzl lists EN 12275 and UIAA on some locking carabiners. Certification does not replace compatibility guidance: use the connector specified by the belay-device maker. Compare tube and assisted-braking devices.
Common questions
Should I use an HMS or D-shaped carabiner with a belay device?
Use the shape and orientation specified by the device manufacturer. HMS shapes provide a larger basket; D shapes are commonly designed for attaching devices to a harness.
Are automatic locking carabiners safer than screw-lock?
They operate differently and each has handling requirements. Choose by the maker's directions, environment and your ability to verify that the gate is locked.
Does a locking carabiner prevent cross-loading?
No. A locking gate does not guarantee correct orientation or loading. Follow the equipment instructions and check the connection during use.
What standards apply to climbing carabiners?
Check the exact connector's label. Petzl lists EN 12275 and UIAA for some locking carabiners; the UIAA standards list calls UIAA 121 Connectors.