Dynamic rope

This is particularly relevant with assisted braking devices, such as the Petzl Grigri (which, for example, works best with a 9.4-10.3 mm thick line[1]) or the Faders SUM.

Users must make sure to read the instructions for the device carefully to ensure safety and recognize any limitations to rope diameter.

[2] The force rating indicates the maximum amount of force the rope can deliver to a falling climber, measured in kilonewtons (kN), under test conditions designed to simulate a hard fall; typical climbing ropes range from 9kN up to an Arborist's 24kN.

Whereas a higher rating (indicating greater strength) is desired for other gear, for dynamic ropes a lower rating is generally desired, as this indicates it would give a 'soft catch' that is less likely to injure the climber or break or dislodge protection or anchors.

[3] Unlike most climbing equipment, dynamic ropes do not have a rated tensile breaking strength.

When climbing, it is possible to produce a fall factor as high as 2, however, real-world climbing situations include additional shock absorbing elements which are not included in the test standard, such as the body of both the climber and belayer, elasticity of their harnesses and anchor materials, and friction between the rope and the belay device, and any protection pieces.

Manufacturers often recommended that ropes be retired if they sustain an extremely hard fall, even if they do not show outward signs of wear.