An apparatus for facilitating measurement of street grades from a top of curb (TC) planar line by a single person, including a pair of hook units, each having a rigid frame structure forming a top segment for resting on a top surface of a respective curb structure, a back segment for engaging a back surface of the curb structure, and a front segment extending from the top segment downwardly and away from the back segment for balancing the unit and for engaging various contoured front curb surfaces. One of the hook units includes a locking spool for tensioning a string line that is connected to the other hook unit. The string line is threaded from the spool unit through an opening in the frame structure in the top segment, the string line extending in contact with the top of the curb, and through a slot in the front segment, the line extending directly toward the opposite curb. At the other hook unit, the line extends through a slot in its front segment, under its top segment in contact with the top of the curb, and through a slot located in the top segment, the string line having a ring tied thereto for removably engaging an outside surface of the frame structure. Each of the frame members is configured for mounting its back segment to a curb- sidewalk interface, the string line extending through the respective frame member from its contact with the top of the curb.
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