Law 24 (5)
Fair delivery - the feet
For a delivery to be fair in respect of the feet, in the delivery stride:
1. The bowler's back foot must land within and not touching the return crease.
2. The bowler's front foot must land with some part of the foot, whether grounded or raised, behind the popping crease.
If the umpire at the bowler's end is not satisfied that both these conditions have been met, he shall call and signal "No-ball".
LEGAL DELIVERY
No problem with this one.
This delivery is clearly legal as the bowler's entire front foot is behind the popping crease.
Remember the umpire has also to keep an eye on what the back foot is doing as well.
LEGAL DELIVERY
Still a fairly straightforward decision for the umpire as the bowler has kept around half his front foot behind the popping crease.
But the official still has little time to make up his mind before he switches his attention to the other end.
LEGAL DELIVERY
This shows how difficult it can be for the umpire.
This delivery is legal because some of the foot is behind the popping crease.
The fact that the foot is raised does not make it illegal.
ILLEGAL
This again shows how tough no-ball calls are to make.
This is a no-ball as none of the foot is behind the crease.
Unlike some other sports touching the line does not count.
ILLEGAL
This should be a relatively straightforward call - it's a no-ball.
But as the Old Trafford Test showed it is still all too easy for the umpire to miss as he tries to concentrate on the business end.