BACKHAND.

Thumb is in line with the shaft, located on the side.

BACKHAND.

Don't extend the thumb too far.

BACKHAND.

The thumb should be relaxed and a slight gap underneath.

FOREHAND.

Stretch the hand forward, so it's diagonally across the grip. That extends the forefinger and the thumb then is between the first two fingers.

FOREHAND.

The side of the thumb rests against the side of the racket. The forefinger curls round the racket.

FOREHAND.

The thumb and forefinger make a V shape.