A Boundary Visualization is a visualization that helps protect you by creating energetic boundaries around you. Boundaries may be visualized with any material (e.g. bricks) or energy (e.g. white light). To build a boundary, visualize an energy wall, a stone wall, or some other sort of fortification around your body, your house, and all those people and things that you wish to help protect.
When visualizing a boundary, do not make it impenetrable to all things. Visualize light energy bolts penetrating and entering, but see slings, arrows, and the dark and icky bolts of the old energy world bouncing off and easily repelled. Visualize many times a day, when you wake and before you go to sleep. The world remains a toxic place. Never forget to protect yourself. Always build and reinforce the boundary.
Be aware that the use of boundary visualizations will, at present time, likely reduce your social experience as all those influences that are any kind of a threat are subtly removed from your personal reality. This is a good thing since it removes negativity, violence, and other albatrosses of spiritual awakening and empowerment.
Finally, although you may be tempted, try not to mourn the loss of darkness, negativity, and violence from your personal sphere, or the realities of this planet. Mourning the loss may create energetic space for the re-entry of these energies and influences, and this is something that you wish to avoid.