Crampons are outdoor footwear that are made from spikes and are worn on boots to provide traction on snow and ice. General-purpose crampons designed for most mountaineering and glacier travel are not well suited for vertical ice climbing. For ice climbing, specialized crampons that provide better support for front pointing are advised. Most crampons require welted boots to ensure proper fitting.
Crampons with 10 points were first introduced by Europeans in the early 1900s. Because they lacked forward pointing spikes, they required step cutting on steep terrain. In the 1930s, two additional forward-slanting points were added, thus creating today's 12-point crampons. While 12-point crampons are now the normal selection, a few 10 point crampons can still be found on the market. The two additional front points further reduced step-chopping and allowed the climber to "front-point" up steep snow and ice. The angles of the first two rows of points also determine the best use for a particular set of crampons. If the first row (front points) bend downward and the second row is angled towards the toe, this reduces calf strain by allowing the boot heel to be lower. In this case, these crampons are better suited for front-pointing. When straight points are used instead, the crampons are much better suited for snow & general mountaineering.
While crampons are an invaluable tool for a mountaineer, they were not used as often as today until the development of plastic-shelled climbing boots, because the straps used to affix the crampons to early mountaineering boots (which were made of leather) had a tendency to restrict bloodflow to the feet of the wearer.
Crampons are usually made of hardened steel, but lighter weight aluminum crampons are popular for alpine ski touring where the need for them is less frequent & counterbalanced by the need for a light pack yielding fast, efficient travel over long distances.
One problem with crampons is that snow can ball up between the spikes, creating a dangerous scenario where the teeth no longer bite into the slope. To prevent this, most crampons can be fitted with "anti-bott" plates: shaped bits of flexible plastic that engage on the body of the crampon.
There are also two types of crampons: hinged and rigid. Hinged crampons provide flex at the instep and bend with the natural motion of walking and thus are the preferred style for almost any type of mountaineering except steep technical ice climbing. A rigid crampon does not bend at the instep so when climbing up steep technical ice, they allow the climber to keep their heel lower when front-pointing, thus less tiring as a result. However, rigid crampons tend to be heavier and will not perform as well in mixed terrain. Generally, most people will use hinged crampons.
In ski mountaineering, climbers will often remove their skis & use crampons on their boots for sections of steep, icy, terrain or technical glacier climbing. Where slopes are sufficiently lower angle for skis to stick, however, they also employ special "ski crampons" that increase the bite of climbing skins, especially on hard or icy snow. To avoid confusion with boot crampons, & because they are far more common in the Alps than in the US, these ski crampons are also known by their European names: harscheisen (German), couteaux (French) & coltelli (Italian).
Crampons are graded C1 C2 and C3. These grades are used to determine compatibility with a walking or climbing boot. Boots are graded B0 (incompatible with crampons), B1 (a sturdy hillwalking boot), B2 (a stiffer mountaineering boot) and B3 (a fully rigid climbing and mountaineering boot). Generally a B3 boot would be compatible with a C3 crampon, a B2 with a C2 and B1 with C1. However a B3 boot can be used with a C3, C2 or C1 crampon, a B2 boot with a C2 or C1 crampon. A B1 boot can only be used with a C1 crampon.
There are three main types of attachment systems for crampons. These include Step-in bindings, Hybrid bindings and Strap bindings.