I think they meant that something striped and rectangular, like a crosswalk, is a 'ruled surface' because the stripes themselves are like the ruler ? So I gues

I think they meant that something striped and rectangular, like a crosswalk, is a 'ruled surface' because the stripes themselves are like the ruler ? So I guess a crosswalk (flat rectangle in 3D space), would be considered a 'ruled surface', but I don't think it meets the other requirement to make it a conoid.