Ski bindings are designed to release the ski boot when a preset pressure occurs. The boot movements that are controlled by the preset are Twist for the toe (front binding) and Forward Lean for the heel (back binding). The preset control is commonly known as the DIN setting. This setting on the front binding allows the toe of the boot to twist out of the binding to help prevent injure. Like wise the rear binding will allow the heel of the boot to pull out with an excessive forward lean.
Now you and I come along with our sitski and we need the opposite affect from the binding. We need the ski to stay on at all time, even in a crash, The ski might break but it will aid in slowing the tumble of a bad crash. In order to minimize the chance of your ski releasing you must pin the binding. Pinning the binding will prevent the manufactures intent for release. By doing this you will void all warranty and liability clam to the manufacture of the binding. You will actually compromise the integrity of the bindings design by drilling a hole through it. But it works, and works well.
There are a few things to realize about mounting bindings for a sitski. You are putting far more stress on the ski and binding then is was designed for. A standup skiers weight is dispersed over two ski and bindings. You are putting all your weight plus the sitski weight on one ski and binding. Use longer screws to get a good bite in the ski. If possible use inserts for all the mounting screws. Pick a good strong wood core ski with some metal in the binding area. Most all high end race skis, and expert all mountain skis meet this requirement.
Out on the mountain you will see pinned bindings with different types of pin. I will show you one way here and explain some others. In the photos we will pin a Marker M38 binding. This is not a high end race binding. It is actually just a good inexpensive rental binding.