A marker has an anchor portion and a twisted portion, and the twisted portion has one or more reflective sides and is twisted about a length axis of the strip so that part of at least one of the reflective sides faces any view toward the marker. Or, a marker includes an anchor portion and a reflective portion, and the reflective portion contains a material that permits manual, plastic deformation to create a twist in the reflective portion. The marker when twisted may be attached to mark a location of a feature of a building in which insulation hides the feature but leaves the twisted portion of the marker exposed within an access space of the building.