Get Outdoors - Mountaineering Basics: Applying Friction: Choosing Methods

Significant trade-off in risks must be considered when choosing a belay method. It is not a straightforward matter of picking the method that enables you to exert the most stopping force, as long as it has no problems of inefficiency, locking up, likelihood of manufacturing defects, and so forth.Static vs. dynamic attempts to stop a fall.

This choice of a general-purpose belay method is sometimes discussed in a confused and confusing way, as though the choice were between "static" and "dynamic" methods of belaying. However, it is not a method of belaying but an attempt to stop a fall that is either static or dynamic: static if there is no run-through, dynamic if there is.

Even if two methods differ significantly in the maximum stopping force you can exert with them, there will be no practical difference at all between them for a very wide range of falls (almost all you will ever have to hold); the falls will be held statically because the force you need to exert will not reach the level at which the rope will start to run with either method.
The situations where the difference between the two methods will mean the difference between the rope running and not running are high-factor falls on high-angle rock with little or nothing to produce friction other than the belay. Still, these are the critical falls, where things are most likely to go wrong.

How to choose a method.

To make a choice of a general-purpose method, it would be helpful to study comparative performance data on belay evices to see which are relatively strong (meaning that the rope will run through the device at a relatively high force), which allow for easy paying out and taking in of the rope, which are easy to lower a climber on, and which can most effectively double as rappel devices.

You may occasionally see published figures that purport to state at what forces the rope will start to run for given devices or methods. All such figures should be viewed skeptically. Even if they are roughly accurate as averages (and many undoubtedly are not), given the great variation in grip strength among individuals and the fact that the actual stopping force of a given device for a given rope in a given condition is related to this grip strength, the average is of little interest.