modernization of elevators, escalators, moving walks, dumbwaiters, material lifts; maintenance of elevators, escalators, moving walks, dumbwaiters, material lifts; repair of elevators, escalators, moving walks, dumbwaiters, material lifts; installation of elevators, escalators, moving walks, dumbwaiters, material lifts; restoration of elevators, escalators, moving walks, dumbwaiters, material lifts