Abstract: A modular apparatus for supporting and guiding a tool such as an ultra-high pressure water jet along a work surface, including a contour following assembly attached to a motorized lift vehicle. The contour following assembly includes a gimbals assembly with an instrument or tool carriage assembly, a positioning assembly that urges the gimbals assembly and the instrument carriage against the surface, and, optionally, a hydraulic, mechanical, or pneumatic pressure system that applies pressure to the positioning assembly. A scissors lift, hydraulic lift, telescoping arm, or other suitable device raises and lowers the apparatus. In operation, the gimbals assembly and the positioning assembly cooperate to maintain the instrument carriage in a user-selected position with respect to a work surface such as a ship hull, aircraft fuselage, storage tank, or the like. Depending on the type of tool selected, the apparatus may be used for cleaning or stripping surface coatings, buffing, painting, washing, and so forth.