Question: Are bindings mounted parallel or perpendicular to run-direction?
About the article "Nordic combined", section "Ski jumping equipment".

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The vast majority of bindings for Alpine skiing work by fixing the ski boot to the ski at the toe and heel.
The binding attaches the boot to the ski, but to reduce injury also allows the boot to release in case of a fall.
Generally, the toe piece is designed to allow the boot to rotate to the sides, while the heel piece rotates up.
In modern bindings a wide variety of motions is available from both toe and heel pieces.
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 amount of torque required to release the boot is adjusted by turning a screw on the toe and heel piece.
This is called (colloquially) the DIN setting, because the standards for Alpine ski binding settings are issued by Deutsches Institut für Normung.
The correct DIN setting is based on height, weight, ski boot sole length, the skiing style of the skier (cautious, average, or aggressive) and, age (if the skier is younger than 10 years old, or 50 years old or older).
Normally, torque itself does not cause injury, not until a natural limit of the human skeleton is reached.
For instance, a very strong vertical torque, twisting the knee, will not cause damage unless the knee is forced to travel beyond a certain angle.
Some bindings move relatively short distances before releasing, leading to the possibly of "pre-release", where the ski releases long before the motion could have caused damage.
Bindings with longer "float" may hold on during events that require those with shorter motion would require higher DIN settings.
Bindings may be sold alone to be mounted to "flat" skis, or can be integrated systems.
Integrated systems have declined in popularity due primarily to their higher weight and difficulty of adjusting the balance of a skier since cants and shims are difficult or impossible to use.
Some racing skis have plates on them which allow a binding to be attached and afford the possibility of changing the balance through cants and shims.
Alpine ski bindings employ the use of a snow brake to prevent the ski from moving while it is not attached to a boot.
Snow brakes work by the use of a sprung square 'C' shape, typically made of metal, which makes contact with the snow.
When a ski boot is put in the ski binding, the brake pivots under the downward pressure and runs parallel with the ski allowing free movement.
When the boot comes out of the ski, the brakes spring out perpendicular to the ski and stop the ski from sliding. 
Snowboard boot bindings are normally screwed onto the snowboard in a permanent orientation which is almost perpendicular to the direction of travel of the snowboard.
When a snowboarder reaches the bottom of a run, the rear boot is typically released from its binding to allow the snowboarder to propel himself forward across relatively flat snow.
Because the front foot in the snowboard binding is at an angle to forward motion, the snowboarder experiences discomfort and tension on his leg, knee and foot joint.
Four to 8 percent of snowboarding injuries take place while the person is waiting in ski-lift lines or entering and exiting ski lifts.
Snowboarders push themselves forward with a free foot while in the ski-lift line, leaving the other foot (usually that of the lead leg) locked on the board at a 45- to 90-degree angle, placing a large torque force on this leg and predisposing the person to knee injury if a fall occurs. 
Binding angle is defined by the degrees off of perpendicular from the length of the snowboard.
A binding angle of 0° is when the foot is perpendicular to the length of the snowboard.
Positive angles are pointed towards the front of the board, whereas negative angles are pointed towards the back of the board.
The question of "how much" the bindings are angled depends on the rider's purpose and preference.
Different binding angles can be used for different types of snowboarding.
Someone who participates in freestyle competition would have a much different "stance" than someone who explores backcountry and powder.
The recent advancement and boom of snowboard culture and technology has made binding angle adjustments relatively easy.
Binding companies design their bindings with similar baseplates that can easily mount onto any type of snowboard regardless of the brand.
With the exception of Burton, and their newly released "channel system", adjusting bindings is something that remains constant among all snowboarders.
Done with a small screw-driver or a snowboard tool, the base plates on bindings can be easily rotated to whatever preferred stance.
One must un-screw the baseplate, pick their degree angles, and then re-screw the baseplates.
Bindings should also regularly be checked to ensure that the screws don't come undone from the movements of snowboarding.
Forward stance: Suitable for most purposes, both feet are angled forward.
Frequently the leading foot is angled roughly 15° to 21° and the trailing foot at 0° to 10°.
A downside is that a rider's balance is notably different when riding in reverse compared to their forward stance.
This can be compensated for by learning how to ride backwards with this stance, also known as riding "switch", or by choosing another stance such as Duck, or Flat stance.
As riders become more experienced, they can experiment with different "stances" to feel what is best for them.
Alpine stance: Used primarily for alpine racing, the leading foot may be from 50° up to around 70° and the trailing foot generally identical or up to 10˚ less.
This gives the rider balance on their board, while angling their feet for best directional control at high speeds.
Duck stance: Useful for tricks by removing the forward bias altogether, the feet are angled outwards in opposite directions, such as 15° for the front foot and -6° for the back foot.
This stance is becoming increasingly popular, and is the most resilient of the three.
The feet do not actually have to be angled equally outwards to be considered duck stance.
The back foot simply has to be angled less than zero degrees.
These angles give the rider a dominant front foot angle at all times which makes it easier for a rider to change the board direction mid-run.
This change in board direction mid-run is called riding "Switch" or "Fakie".
Duck stance is also very popular for park riders because it gives them the versatility to move their board in all directions.
It is easier to spin, balance on rails and boxes, and land "switch" when one's feet are both angled outward.
The degree of the angle depends on the individual.
Flat stance: Also popular with riders who wish to have a consistent stance riding forward or backward, a flat stance is simply one in which both feet are at a zero angle, or perpendicular to the length of the board.
This may result in "toe drag" on narrower boards or if the rider has larger feet, in which the rider's toes overhang the edge of the board and may contact the snow during sharp turns on the toe side of the board.
The "Flat" Stance is no longer popular and is not recommended by the AASI (American Association of Snowboard Instructors).
Riders who use the flat stance will commonly experience pain in their ankles and calves when turning toe-side and heel-side.  
General fundamental quantities.
A wave can be longitudinal where the oscillations are parallel (or antiparallel) to the propagation direction, or transverse where the oscillations are perpendicular to the propagation direction.
These oscillations are characterized by a periodically time-varying displacement in the parallel or perpendicular direction, and so the instantaneous velocity and acceleration are also periodic and time varying in these directions.
But the wave profile (the apparent motion of the wave due to the successive oscillations of particles or fields about their equilibrium positions) propagates at the phase and group velocities parallel or antiparallel to the propagation direction, which is common to longitudinal and transverse waves.
Below oscillatory displacement, velocity and acceleration refer to the kinematics in the oscillating directions of the wave - transverse or longitudinal (mathematical description is identical), the group and phase velocities are separate. 
 Bindings
 The binding must be mounted parallel to the run-direction.
The binding must be placed in such a way that a maximum 57% of the entire ski length is used as the front part.
 Boots
 High-backed, flexible yet firm boots with a low cut at the front.
They are designed to allow the skier to lean forward during flight.
 Connection cord
 Part of the binding; a cord that attaches the ski to the boot and prevents the wobbling of skis during flight.
 Ski jumping suit
 All portions of the ski jumping suit must be made of the same material and must show a certain air permeability.
The size of the suit must conform to the body shape in an upright position with certain tolerances.
 Jumping skis
 Jumping skis are manufactured especially for use on ski jumping hills.
Skis with a length of a maximum 146% of the total body height of the competitor may be used.
The curvature and shape of the skis is restricted by certain geometric features.