Fundamental functions such as domain stabilization, vertical Bloch line (VBL) pair propagation, and VBL pair injection for the Bloch line memory were experimentally investigated. A ring-shaped domain has been developed which gives a propagation track for VBL pairs. Selective grooving of the magnetic film surface provides for formation and stabilization of the ring-domain. A VBL pair has been propagated by a local in-plane field. VBL pair separation and recombination by an in-plane field was also successfully carried out. A method for VBL pair injection into the domain wall has been developed. This method utilizes the horizontal Bloch line (HBL) punch-through at the flank wall and successive domain chopping. The method is more practical than pushing the stripe domain head.