Call it ?knitted graffiti? — an unusual art installation in Madison. On a busy State Street intersection, staff and students from the UW School of Human Ecology were busy ?yarn bombing? all day Thursday — covering a Metro bus shelter in knitting. Lisa Frank, interim director of the school?s Design Gallery, said the installation has been in the planning stages for months, but the actual knitting has taken place over the last three weeks or so, by members of the Madison Knitters? Guild.