A simple way to perform the single haul cast is to grasp the line and to hold it stationary downwards at your side during the backcast. The rod hand movement pulls the line back as it moves through the backcast stroke. (See Diagram 1)
This is a very efficient casting method. In a timely manner the line is pulled back automatically on the backcast; it enhances the backcast by increasing its line speed. Backcasts are weaker than forward casts, and the single haul helps strengthen the backcast.
A true single haul takes this pulling back on the line during the backcast
one step further by having the line hand pull down at the same time as the backcast stroke is made. Additional line momentum is created giving the backcast higher line speed. Remember the line must be straightened out before it can be cast; a straightened backcast line is easier to cast on the forward cast. (See Diagram 2.)
I use one of these single hauls on every cast because it greatly improves my backcast. This haul is timed to occur during the last half of the casting stroke. It is a short fast downward pull by the line hand that complements the smooth acceleration stroke.