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A ski binding is a device that connects a ski boot to the ski. Generally, it holds the boot firmly to allow the skier to maneuver the ski. However, if certain force limits are exceeded, it releases the boot to minimize skier injury, such as in the case of a fall or impact. There are different types of bindings for different types of skiing.
Modern alpine skiing bindings fix the boot at the toe and heel.
To reduce the possibility of injury the bindings can release in case of a fall. The boot is released by the binding if a certain amount of torque is applied, usually created by the weight of a falling skier. The torque required is adjustable, according to the weight, foot size, and skiing style. A snow brake prevents the ski from moving while it is not attached to a boot.
An alpine touring (or randonee) binding allows the skier to have the heel of the ski boot free and the toe of the ski boot in the binding when using Nordic skiing techniques for ski touring, and to have both the heel and the toe of the ski boot in the binding when using alpine skiing techniques to descend the mountain. Most touring bindings are designed for ski boots falling under one of two ISO specifications:
- ISO 5355:2019, for traditional alpine boots. In this variation the pivot is located in the front of the binding.
- ISO 9523:2015, for boots in which the pivot is formed at the boot / binding interface.
The two setups are typically incompatible in that the principal by which they affix the boot to the ski is different.
The cable binding was widely used through the middle of the 20th century. It has the toe section of the boot anchored, and an adjustable cable around the heel secures the boot. While binding designs vary, before 2007 almost all dedicated Telemark models had been designed to fit boots with 75mm Nordic Norm "duckbill" toes.
Rottefella (NN, Nordic Norm)
The Rottefella binding was developed in 1927 by Bror With. The name means "rat trap" in Norwegian. It is also known as the 75 mm, Nordic Norm, or 3-pin. After victories at the 1928 Winter Olympics in St. Moritz, the binding remained the standard for cross-country skiing for the next 60 years. They are no longer as popular as they were but are still for sale. The binding has three small pins that stick up from the binding. The toe of the boot has three holes into which the pins are inserted. The boot is then clamped down by a bail. The binding is asymmetrical, having left and right foot orientations. Prior to the Nordic Norm, cross-country ski bindings had as many as four pins.
NNN (New Nordic Norm)
Rottefella's NNN (New Nordic Norm) has a bar in the toe of the boot hooked into a corresponding latch in the binding. There have been several versions of NNN, and the first NNN version is not compatible with current designs. A stronger, wider BC (Back Country) version also exists, abbreviated NNN BC or NNN–BC.
NIS (Nordic Integrated System)
NIS (Nordic Integrated System), introduced in 2005 by Rossignol, Madshus, Rottefella, and Alpina, is fully compatible with NNN boots and bindings, but is a different way of attaching the bindings to the ski. It features an integrated binding plate on the top of the ski to which the bindings attach, allowing adjustment in the field with a metallic NIS key. The initial design of the plate used a movable insert for position adjustment. NIS skis allow installation of non-NIS bindings. In 2007, Fischer abandoned SNS and entirely switched to NIS.
Rottefella Xcelerator bindings provide an increased power transfer from ski boots with a matching Xcelerator pattern sole. Xcelerator SSR bindings include QuickLock mechanism for tool-less position adjustment.
SNS (Salomon Nordic System)
SNS (Salomon Nordic System) looks very similar to NNN, except it has one large ridge and the bar is shorter. Three variants exist:
- SNS Profil: One metal bar in the toe of the boot.
- SNS Pilot: Two metal bars on the boot.
- SNS X-Adventure: Stronger design used for back-country skiing (also referred to as SNS–BC).
Pilot boots cannot be used with a Profil binding but Profil boots can be used with Pilot bindings. The original Pilot boots had the front pin 10 mm from the front of the boot (RS10), while the newer Pilot boots have the front pin 17 mm from the front of the boot (RS17). SNS is marketed by Amer Sports under their Salomon and Atomic brands.
The predecessor was simply called Salomon Nordic System (SNS):
- SNS: "U-shaped" metal bar protruding from the front of the boot
The Rotefella NNN system was adopted by Fischer and their various brands, making SNS decline in use in North America. In response to the need for NNN compatibility, in 2016 Salomon introduced the Prolink system, although Salomon claims that SNS will still be produced and available. The Prolink binding is somewhat lighter than NNN and mounts directly to the ski using pre-drilled holes, as opposed to a built-in ski-mounted NIS or IFP plate used by NNN. Salomon claims their new system delivers a superior “snow feel” as compared to NNN or even their own SNS system which pairs with thicker soled boots.
NTN (New Telemark Norm)
In 2007, Rottefella introduced the New Telemark Norm binding. The system's objective is to provide a free heel telemark ski binding featuring lateral release, increased lateral rigidity, tunable performance, and free-pivot touring functionality. The boots are unlike other tele boots in that they do not have a 75 mm square toe and require a lip underneath the arch of the boot for the binding to attach. Scarpa sells a version of the boot which is compatible with NTN Tele and Dynafit bindings. Rottefella currently (2015) offers two models of the binding, the Freeride for the lift assisted skier and the Freedom for the tourer. Both models feature a free pivot and one boot standard, NTN. Different spring cartridges can be used to match the binding to the skier's weight and skiing style.
In 2016, Fischer and Rossignol introduced a new IFP (Integrated Fixation Plate) binding plate which allows tool-less adjustment of binding position. The Turnamic binding uses step-in locking for the boot, and the lock closes or opens by turning the lever to the side.
The IFP Turnamic bindings can be used with all NNN/Prolink boots, but the IFP plate will not accept NIS 1.0 bindings because of the new lock mechanism.
Rottefella subsequently introduced continuously adjustable MOVE Switch bindings which can be installed in the IFP (and NIS) plates.
NIS 2.0 (MOVE)
In 2018, Rottefella and Madshus announced the NIS 2.0 plate with the MOVE bindings which allow continuous on-the-fly adjustment of binding position with the boot locked-in. The NIS 2.0 plate and the MOVE Switch turnable wheel are designed to accept any existing NIS/NNN binding, using either fixed inserts or adjustable sliding inserts. MOVE Electric remote adjustment is being developed for 2019-2020 season. Rottefella also provides MOVE Switch conversion kits for NIS 1.0, IFP, and Prolink skis. 
The use of continuously adjustable bindings has been approved by the FIS; such adjustment allows the skier to fine-tune ski grip and glide, which is important for classic style racing on skis with waxless "mohair" grip-zones. Previous Rottefella NNN bindings required the skier to dismount then apply significant force to a small metal NIS key to unlatch the binding.
In the early days of skiing, the binding was similar to those used on snowshoes: a leather strap fastened over the toe of the boot.
- 1840s: Sondre Norheim demonstrated Telemark skiing before 1866, and the Open Christiania in 1868, both made possible with a binding design (which dated back to the late 1840s). This added a loop of twisted birch roots that ran from the existing birch root toe loops around the boot heels and back. This allowed the heel to lift as before, for walking and gliding, but better held the boots to the skis allowing greater control. This enabled Norheim to control the skis with his feet and legs, replacing the former technique of dragging a large pole in the snow on one side or the other to drag the skier in that direction. These new techniques spread throughout Telemark and would later be named for the region.
- 1894: Fritz R. Huitfeldt invented a binding with a secure toe iron which allowed the heel to move freely. This became the standard industry binding through the 1930s. Huitfeldt drove the evolution of the ski binding over the next 20 years. In 1894, he introduced the use of semi-circular metal hooks at the toe to attach the straps. The hooks were positioned to tightly fit to the sides of the boot, keeping the ski centred and eliminating any "flop" that the formerly loose straps allowed. The heel strap was also attached to the same hooks, but because of their rounded shape, the required range of motion was provided by the straps sliding up and down on the hooks. This allowed the heel strap to be replaced by a less flexible leather strap. Together, these changes dramatically tightened the binding, greatly increasing control.
- 1897: Huitfeldt further improved the design by changing the toe piece. Instead of hooks, he drilled a rectangular hole through the ski from side to side, and passed an iron bar through it. The bar was then bent up on either side, locking it in place, and then formed to fit the toe of the boot. This improvement once again dramatically improved the firmness of the fit. Finally, in 1904 he adopted the Hoyer-Ellefsen toggle, a lever that replaced the buckles. This not only greatly improved mechanical advantage, further improving the strength of the binding, but also made the system much easier to put on and remove. Better yet, the geometry of the attachment points meant the heel strap was mechanically attached below that of the toe strap, which provided a constant "diagonal downpull" that naturally returned the heel to the ski.
- 1920: Huitfeldt style bindings were by far the most popular system for decades, with the only major change being Marius Eriksen's 1920 introduction of pre-formed plates that were screwed on top of the ski. Other binding systems did exist, in particular a class of bindings originally introduced by Mathias Zdarsky that replaced the heel strap with a long metal plate under the sole of the boot, hinged at the front to allow the heel to rise. The heel was held to the plate by a short strap attaching at the back. These gave even better control than the Huitfeldt design, but so firmly attached the leg that injury was a real problem.
- 1927: Change eventually came through the evolution of the Rottefella binding, first introduced in 1927. The original Rottefella eliminated the heel strap, which held the boot forward in the binding, by drilling small holes in the sole of the boot which fit into pins in the toe piece. This would only work if the sole was held very firmly down on the pins, so the binding also introduced a metal clip that was forced down onto the top of the sole of the boot, forcing it onto the pins. When the inventor, Bror With, won a race on the new design, Norwegian Crown Prince Olav asked him what they were, and he responded "Oh, they're just a couple of rat traps I picked up at the hardware store". "Rottefella" is Norwegian for "rat trap".
- 1929: The introduction of the cable binding allowed the Christie turn to become a standard on downhill runs, and to further support this style of skiing the Swiss racer Guido Reuge in 1929 invented a cable binding with steel clips below the boot heel to enable clamping the heel down for downhill portions. He named the product "Kandahar" for the international Kandahar Cup ski races. In use in alpine races, the Kandahar binding led to serious leg injuries, and by 1939 experimentation began in earnest on bindings that would release the boot in a fall.
- 1932: a major advance on the Huitfeldt concept was introduced to the market by Guido Reuge in 1932. Reuge replaced the heel strap with a metal cable connected to a spring at the front of the toe. The spring provided even tension as the boot moved. Previously, the strap was adjusted so it had enough slack to allow the boot to rotate as high as the skier wished, but as the boot rotated back down to the ski it became increasingly slack again. The cable removed this limitation, and held the boot firmly through its entire motion, greatly increasing the solidity of the fit. A later advance added two small metal clips near the rear of the foot that the cable could be clipped under. These held the boot firmly to the ski during downhill portions of the runs. Cable bindings remained in use for some time for cross-country, and are today popular for telemark skiing. However, the Rottefella design from the 1930s became more popular for Nordic skiing through the 1950s and into the 1970s until the Salomon Nordic System (SNS) binding entirely re-invented bindings used for Nordic skiing.
- 1937: Hjalmar Hvam broke his leg skiing, and while recuperating from surgery, invented the Saf-Ski toe binding, which he later sold under the slogan "Hvoom with Hvam". This was a metal clip with a pyramidal top that fit into a slot cut into the sole of the ski boot. When the boot was rotated forward, the slot on the toe eventually rose above the metal pyramid, allowing the toe to release from the ski. The system was considered with suspicion by professional skiers, especially when Olaf Rodegaard released during a race. However, Rodegaard credits the release with saving him from a broken leg. In the post-war era, Hvam sold several thousand pairs of Saf-Ski's, in an era when alpine skiing was in its infancy. Hvam continued to sell the Saf-Ski into the 1960s, but in 1966 his insurance rates increased so dramatically that he was forced from the market.
- 1950: A dramatic advance in alpine ski bindings was introduced as the Look Nevada in 1950. The Nevada held the toe centred over the ski using two metal fingers shaped into an upside-down V. The fingers were pivoted to allow motion to the sides, and centred with a spring. During a fall, sideways torsion could overcome the force of the spring and allow the boot to release directly to the side. This design was quickly copied by other vendors, notably Marker, and had the first real impact on the dominance of the fixed-toe bindings. By the late 1950s, there were about 35 different release toe bindings on the US market, most of which used a normal Kandahar-style heel cable.
- 1960: The first modern heel-and-toe binding for alpine skiing was the Cubco binding, first introduced in 1950 but not popular until about 1960. A heel-release binding faced the problem that there was no obvious place to attach to on the heel, so the Cubco solved this by screwing small metal clips into the sole of the boot. This also eliminated the changes in performance as the sole of the boot wore down, or the geometry of the sole changed as the boot wore into the skier's foot. Marker introduced the Rotomat, which gripped onto the sole where it extended past the heel, and Look quickly followed suit with their Grand Prix design. By the mid-1960s, release bindings that worked on both the heel and the toe were common, and by the late 1960s, the cable binding had disappeared from alpine skiing.
- 1966: The introduction of plastic ski boots permitted the development of industrial standards for the function of alpine skiing bindings.
- 1972: Injury rates from alpine skiing began to fall with the gradual introduction of the Teflon anti-friction pad around 1972.
- Alpine: One problem with 1960s release bindings was that the boots were not standardized, and a binding that worked well on one boot might be dangerous on another, or might become dangerous over time as the boot shifted about. This led to the introduction of plate bindings, which used a metal plate firmly clipped to the sole of the boot, and bindings that clamped onto the plate. The plate could be easily removed for walking about. Plate bindings were popular in the US in the 1970s, notably the BURT Retractable Bindings and Spademan binding, but never caught on in any major way in Europe. As more and more of the alpine skiing market came under control of European companies, the plate bindings disappeared, in spite of their excellent safety records. The disappearance of the plate and alternate systems was due to a combination of factors, notably the introduction of standardized hard plastic boots. Plastic was first introduced by Lange as a way of improving existing leather designs. As the new material spread through the industry, the sole piece was standardized to allow toe-and-heel bindings to clip on. Plastic had the advantages of being much firmer than leather, not changing shape over time, and having predictable friction characteristics wet or dry. Although plate bindings of the era had much better safety records, notably the Spademan design, the new boots and bindings could be easily adapted to any ski for any skier.
- Nordic: Problems with the geometry of the boot sole, which meant only certain boots would work, meant the Rottafella was not widely used. This problem was eventually solved through the same evolution of plastic components that changed the alpine skiing market. The use of highly flexible plastics allowed for a sole that was very strong torsionally and side-to-side, but still had excellent flexibility lengthwise, allowing the heel to rise as with a cable binding. This was standardized as the 3-pin system, which was widespread by the 1970s. A similar system with a 50 mm "duckbill" once existed for lighter setups, but is obsolete and no longer available. Unlike the 75 mm it was symmetric. It was the binding of choice for racing, before the adoption of skate ski racing, in the early 1970s. The 50 mm was also designated according to the thickness of the "duckbill" having either 7 mm or 11–13 mm thick soles hence these bindings often had two notches in the bail to clamp boots with different sole thicknesses.
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Media related to Ski bindings at Wikimedia Commons