Reference lines were introduced from Release 7 of Revit. Its purpose being, to set up angle parameters. Reference lines together with an angular dimension parameter, control any geometry attached to the angular reference. For example, the web of a truss. Reference lines also provide two planes, one parallel to the plane the other perpendicular to the reference plane. Although reference lines cannot be named, one can use these two planes to create a Work Plane from.
After selecting the Work Plane tool, select “Pick a plane”, in the Work Plane dialogue box. By using the Tab Key, filter through the selection of the two which you would like to set as current.