The Black Lives Matter Memorial fence was a temporary chainlink fence installed in the area north of Lafayette Park and the White House from June 2, 2020, until January 30, 2021. The fence prevented public access to the area, and it also served as an important site of protest and self-expression. 

Activist Nadine Seiler played a crucial role in protecting and caring for the fence, along with Karen Irwin and other activists in a loosely-formed group informally known as the "Guardians of the Fence." Nadine Seiler and Aliza Leventhal systematically documented the fence over the course of months, and Seiler became the de facto curator of the fence. 

Additional information: 

Library of Congress blog post "Protest Preserved: Signs from D.C.'s Black Lives Matter Memorial Fence" 

D.C. Public Library Black Lives Matter Memorial Fence Artifact Collection”