The bridge hand is very much underrated, as it’s more than just a bridge controlling the direction of the cue. However, let’s start from the beginning.
 

The bridge hand requires the fingers to be distanced to offer stability to the bridge itself. The thumb is tucked against the knuckle of the first finger. The knuckles should be slightly raised. And this is basis of the bridge hand.
 

But now let’s add to the requirements of the bridge hand.
 

When a player is in the cueing position, it is important that the player replicates and standardises this position. There is many a time that I see players adjust their cueing position due to playing shots with bottom, top or stun. But if a player maintains the same exact position for the majority of each shot, they would reduce error and they would standardise their cueing. So if a player adjusts their bridge depending on where they are hitting the cue ball, the cueing position can remain the same. For instance, a low bridge would be for hitting the bottom of the ball and high bridge would be for hitting top on the cue ball and so on. This creates a standard cueing position which helps with playing through the ball on a regular basis.