Abstract: The present invention provides an improved mechanical coupling for rapidly adjusting the elevation of a working edge portion of a tool which working edge portion is subject to wear that decreases the effective length of the working edge portion. In one embodiment, the bristles of a drum-type brush comprise the working edge portion. Once the working edge is properly adjusted with respect to a work surface, the amount of downforce imparted by the working edge and the pattern of the working edge on a work surface are maximized. In use an operator compares the length of the working edge to a first indicia set displayed adjacent the working edge and adjusts the elevation of the working edge with reference to a second indicia set which corresponds to the first indicia set. Surface maintenance vehicles which support an adjustable height tool with a working edge that wears down may utilize the present invention.