A large selection of mechanical plant is now available as an aid to building and civil engineering work. Much time can be saved by the proper use of mechanical aids and this may lead to savings in cost, but the full advantages can be obtained only if the plant is well managed both on the site and off. This Digest summarizes the various costs arising in the use of plant as a guide to its management and utilization. It is based on surveys by BRS of the costs of owning and running contractors’ mechanical plant.