Abstract: A flexible, visual boundary marker is provided for delineating surface boundaries and allowing unobstructed transgression of the boundary. The marker of the present invention is particularly useful on a golf course since the marker can be run over by either reel or rotary type lawn mowers without sustaining permanent damage. In this manner the turf immediately adjacent the marker can be maintained without the need to temporarily remove the marker or to maintain the adjacent turf with an additional hand tool. The marker has a highly prominent flag fixed to an elongated post which stands vertically in a free-standing orientation, flexes to a horizontal orientation when contacted by a surface maintenance vehicle such as a lawn mower, and which returns to a vertical free-standing position after the vehicle has transgressed the marker. The marker resists permanent damage, even from commercial reel or rotary lawn mowers, due to the dimensions and flexibility of the marker.