The preceding description shows what form of hill is most desirable, and is always chosen for competition purposes where big jumps are to be made. It is by no means on a hill of this shape alone that a jump can be made; and for learning, when you will only jump a short distance, almost any hill will do, provided the ground be fairly smooth and the slope below the platform and the level outrun beyond it be long enough.
If the shape of the hill in section is convex, as in the diagram, the best place for the platform, as already explained, is at or near the point where the angle changes, provided always that the steeper part of the hill is fully ten yards longer than the longest jump you will make. If it is a little less than this, build the platform farther back; if much less, choose a slope where there is no change of gradient.
The slope below the platform, or, at any rate, all of it except the part which the jumper would be certain to clear, must be free from irregularities, have a good covering of snow (at least a foot when beaten down), and fall at a steady gradient of not less than 20° for choice—if possible of more.
The platform itself may be built in different ways; the high platforms used in competitions are generally built of planks supported at the outer corners by posts.
This is unnecessary in the case of a low platform, such as you will use at first.
A simple way of making it, if the materials are handy, is to lay two or three planks on top of an old packing case, and then to shovel snow over them. Another way is to stand two short sticks upright in the snow at the same level, and a yard or so apart, according to the intended width of the platform. Stack fir branches against them on the uphill side, and then build a platform of snow, or alternately snow and branches, piling it high enough to rise well above the tops of the upright sticks. Beat it down with the spade and stamp it with the skis until it is quite solid.
For learning, the platform should at first be quite low—not much more than a foot high at its front edge.
For big competitions, the platform is generally 6 or 8 feet high, or even more, though Huitfeldt, a Norwegian authority, says it should hardly exceed 3 feet.
Raising the platform, while increasing the length of the jump, also increases the shock of landing, and therefore the difficulty of the jump. This difficulty, however, depends far less on the height of the platform (which may, so to speak, be merely a negative quantity, for of course it is possible to make the platform look high by cutting away the hillside below it without affecting the nature of the jump) than upon the difference between the angle of its surface and that of the slope below, the most difficult kind of platform to jump from being that called by the Norwegians a “Spraet Hop” (squirt jump), which is higher at its front edge than where it joins the hillside. At first, therefore, make the platform at almost the same angle as the slope below, and join it gradually to the slope above, so that there is no sudden change of gradient.
The length of the jump depends not only on the height, position, and angle of the platform in relation to the slope, but also on its absolute angle in space. Other things being equal, a platform sloping downwards at an angle of between five and ten degrees permits the longest jumps. It would be easy to find by experiment exactly the most favourable angle, and, for all I know, this may already have been done.