We used to play like this:
3-4 boys stand in a circle, maybe 6ft in diameter.
The knife is thrown by the first boy to stick, hopefully, point first into the ground. Without moving the other foot, the boy on his right has to move his nearest foot up to the knife, pull it out of the ground and then it's his turn.
But, if the knife doesn't stick in point first, the thrower has to move his foot up to it, retrieve the knife and pass it to the boy on his left. This tends to guard against stupidly long throws.
The aim of the game is to make your opponents either fall over because their legs are too far apart, or make them unable to move their foot up to the knife to retrieve it. Either of these means that player drops out and the survivors continue. Last man standing is the winner.
I've also played a "chicken" version of this were the knife has to stick in between the opponents feet, the nearest foot is moved inwards and the game progresses. If the knife does not stick in properly the thrower has to halve the gap between his own feet. As time goes on the throws get more and more risky as the space between the feet narrows. I could not recommend this version of the game, especially if played with my old schoolmates.....
Rat