You can split a humbucker by connecting a lead wire to the two finish wires in each coil. When you connect the lead wire to ground, it shorts one of the coils out leaving one coil operative. When you split a Gibson style humbucker, the stud side or non-adjustable side is operative and the adjustable side is shorted out. If the beginning and finish wires are reversed, the stud side is shorted out and the adjustable side is operative.