Abstract: A flexi-rail assembly for supporting and positioning tools for inspecting a nuclear power plant steam generator. The flexi-rail assembly includes a housing; at least one lock assembly carried by the housing for coupling the housing to a support structure; and a carriage assembly movably supported by the housing for supporting and positioning inspection tools such as a robot manipulator arm and leg assembly. The housing includes a hollow rear portion for receiving at least one cylinder supporting a movable surface, wherein the cylinder is coupled to a source of pressurized fluid. The housing also supports at least one recessed surface for receiving the lock assembly. The lock assembly includes the cylinder and at least one tubular member. The tubular member includes an open center and at least two openings formed in the surface of the tubular structure.