 The repairs of the public works and the keeping of them in proper condition were let out by the censors by public auction to the lowest bidder, just as the "vectigalia" were let out to the highest bidder.These expenses were called "ultrotributa", and hence we frequently find "vectigalia" and "ultrotributa" contrasted with one another.The persons who undertook the contract were called "conductores", "mancipes", "redemptores", "susceptores", etc.