A Demonstration of the Open Bridge and the Rail Bridge
The following video demonstrates how to form an open bridge and a rail bridge. Depending on the cue ball position on the table, a different bridge may be called for.
When the cue ball is in the open center of the table, the open bridge will often be used. When the cue is along the rail, the rail bridge may be a better choice. The cue stick is best played at a parallel to the table bed, so the choice of bridge will be determined by this consideration.