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. The work surface may comprise any finished or unfinished interior or exterior surface such as without limitation such surfaces covered with fabric, carpet, tile, wood, stone resin-based and plastic materials and the like.