This is how the pulley rig looks in the  water (imagine bait on the hooks).  The trace flows gently in the
current.

When the fish takes the bait it will not feel the weight  of the sinker until the whole rig has slid down to the sinker.  This gives the  fish more time to take the baited hook properly before the whole setup sets the  hook
automatically for you.  All you have to do is give a nice gently tug to  make sure the hook is set properly and then bring the fish in.