It was a big job, in the first place, to determine exactly how men should be classified. After the classification had been decided upon, it then became necessary to devise simple, rapid, and accurate methods of placing every enlisted man in the Army in his proper classification, and then of so indexing three or four millions of men that any particular demand could be met. For example, one camp might ask for three farriers, nine sanitary engineers, two car carpenters, six boilermakers, and a pipe fitter. It was necessary that some system be perfected to permit of the filling of this order instantly by taking the men qualified to perform these duties out of the camps where they were undergoing military training. The whole system had as its basis a card for each soldier, on which, by a simple system of marginal numbers, punch holes, and coloured index tags the record of each man’s precise ability was kept. Every man, as he was inducted into the service, was required first to make a preliminary, rough classification of himself—that is to say, he recorded himself as a tailor, a blacksmith, or a milk wagon driver. But the Trade Specifications Index was as precise in its detail as a dictionary. It was, in fact, a collection of definitions of what was meant by occupational titles which had vague or various meanings in different parts of the country. Thus, a man might have classified himself as a tailor who, if called upon to make a uniform, would have been unable to do so. Tailoring had to be subdivided, from simple pressing and repairing up to expert fitting. One might be a good coat maker while another had never worked on anything but trousers. So there was devised a system of trade and occupational tests to which every man claiming skill at a trade was subjected, and which determined, as nearly as it is humanly possible to do, exactly the degree and kind of vocational skill possessed by every man in the Army. When the problem of formulating tests was analyzed, it was seen that certain requirements were fundamental. Trade tests to be absolutely satisfactory, 1. Must differentiate between the various grades of skill; 2. Must produce uniform results in various places and in the hands of individuals of widely different characteristics; 3. Must consume the least amount of time and energy consistent with the best results. Now it must be recognized that trades useful in the Army are of many kinds and of widely differing requirements. Trade ability in any one of them, however, means about the same thing. It means that the workman is not simply the possessor of a single item of information, nor simply able to execute one particular movement required by the trade, but that he has many items of information more or less systematized together with the ability to execute various movements not only singly but in combinations.