سكين - Ice Knife

When negative pressure pushing down on the spine is applied to the blade all the stress is transferred from the hook on the blade's tang to the hook on the rocker bar and thence to the small rocker pin.

This involves heating the steel above its critical point, then the blade to harden it.

When the knife is open a spring biases the bolt to the forward position where it rests above the tang of the blade preventing the blade from closing.

As early as 1646 reference is made to a superstition of laying a knife across another piece of cutlery being a sign of witchcraft.