Low Friction (Slick) Belay Devices
Slick belay devices offer less friction than other belay devices, allowing the ropes to pass through the device with greater ease. The advantages of this are that a falling climber will come to a gradual stop, putting less strain on their body and the equipment. This is useful for traditional climbing where protection is poor or where a lead climber is taking large falls. The disadvantage of a slick belay device is that it is more difficult to stop a falling climber, and hold them in place once they have fallen. Recommended for experienced climbers only.
Intermediate Belay Devices
Intermediate belay devices are the most common type of belay device, trying to be the one-size-fits-all device. Their purpose is to reach a ‘middle ground’ where ropes pass freely through the device, but at the same time offering enough friction to easily stop a falling climber. Intermediate belay devices are perhaps the most versatile, lending themselves to a number of situations, although not excelling in any.
High Friction (Grabbing) Belay Devices
Grabbing belay devices offer more friction than intermediate or slick devices making it easier to hold a falling climber. They are useful for novice climbers who require more assistance from the belay device, when belaying a heavier climber, or belaying a climber who is likely to be hanging on the rope for extended periods of time. The disadvantages of grabbing devices are that in the event of a fall, they place a greater impact on both the equipment and the falling climber, and it can be difficult to pay out rope to a lead climber.
The majority of belay devices on the market today are suited to climbing with two ropes. This is useful to prevent rope drag when placing protection in traditional climbing, or for providing greater friction when abseiling.
Some belay devices have just one slot for a single rope. Autolocking devices such as the Petzl Grigri are a typical example of this, however, there are some standard belay devices for single ropes such as the Edelrid Jul. The advantage of this type of belay device are that they are better suited to thick sports ropes. The standard single rope belay devices are also cheaper than their twin rope counterparts. The disadvantage is that you are limited to climbing with a single rope. Recommended for indoor climbing walls or bolted sports crags.
The belay device will accommodate thicker ropes (9-13mm).
The belay device will accommodate thinner twin/half ropes (6-9mm).
Autolocking Belay Devices
The autolocking belay device can catch and hold a falling climber with little assistance from the person operating the device. This makes it useful for when the climber will be hanging on the rope for extended periods of time. The disadvantages of autolocking devices are that in the event of a fall, most devices in this category create large impacts on the equipment so are better suited for sports/indoor climbing, most only work with thick single ropes, they can be difficult to operate, they are not as versatile as other devices, and they can be expensive. Recommended for experienced climbers only.
Autoblocking Belay Devices
Not to be confused with autolocking.
When used from above, Autoblocking belay device can catch and hold one or two falling climbers with little assistance from the person operating the device. Because autoblocking belay devices don’t need to be attached to the belayer’s harness, they make it easier to escape the system in the event of an accident, and they place less strain on the person belaying. They are useful for guides and instructors who might be working with two clients at a time, experienced climbers climbing with inexperienced climbers, or when belaying a heavy climbing partner.
Lightweight Belay Devices
The weight of a belay device is usually measured in grams. How important it is to have lightweight equipment depends on the type of climbing it is used for. For indoor/sports climbing, this is of little concern. For multi-pitch traditional climbing it is beneficial to reduce the overall weight of the equipment being carried.
As the rope passes through a belay device, such as when abseiling or lowering a climber from the top of an indoor or sports route, heat is generated. This heat can be harmful to the device, the rope, and yourself. More heat than usual is created when belaying more than one person at a time, or during long abseils. In both situations, a belay device which is able to remove this unwanted heat is preferable.