The mark consists of a three-dimensional rectangular staging platform comprising a contoured frame around the circumference of the platform. The frame includes four lipped protrusions forming two grooves along the circumference of the frame where a first lipped protrusion at the bottom of the frame projects upward, away from the bottom of the frame, and a second lipped protrusion projects downward toward the first lipped protrusion. A third lipped protrusion, above the second lipped protrusion, projects upward toward the top of the platform and a fourth lipped protrusion projects downward toward the third lipped protrusion. Between the second and third lipped protrusions a fastener is located at each end of the platform edges. One locking mechanism is located on the shorter side of the platform along the upper edge of the frame, and two locking mechanisms are located along the longer side of the platform along the upper edge of the frame; each of the locking mechanisms is above the fourth lipped protrusion.