To qualify for the long jump you have to stay behind or on the blue board. If you go over you automatically get a scratch. Three scratches and you're out.
The only offical rule is to jump behind the board. All others are technical rules that only the IAAF knows (steroids etc.).
back of the board for your approach and front for the jump
step over the white board you jump of from.
When you either step past where your not supposed to or you don't jump close enough to the board
The long jump is measured from the front of the jump board to the closes point in the sand that the jumper touches the sand in a straight line.
When you go past the board with your feet.
5 metres exact