Let us take for the sake of argument a shell body. If after being turned to presumably the required and finished diameter it was found to slip through the hole of a "not to go" working gauge, there was no alternative other than that of scrapping it then and there, because obviously once turned to too small a diameter, not "all the king's horses nor all the king's men" could ever increase that diameter by one single iota again; as a biblical parallelism one might even add that it would be "easier for a camel to pass through the eye of a needle" than for a "not to go" shell to enter into bond. If, on the other hand, the shell would not quite enter the "to go" hole of a "working" gauge, or even if it was a tight fit in this hole, it followed that there remained a certain tolerance or margin whereby the diameter could still be reduced to a trifle, and the shell _per se_ qualified as a candidate for the final examination of the "inspecting" gauge. Picking up, then, our "inspecting" gauge we find that this, in like manner, has two holes, one "to go" and one "not to go"; but the gauge-maker has perforce been wily enough to leave the tolerance of these "inspecting" gauge holes a minute fraction of an inch greater, above and below the required finished dimension, than that allowed in the "working" gauge holes, his purpose being to ensure the inspector something up his sleeve in the way of control over the machinists who use the "working gauge" only; hence the "not to go" hole of the "inspecting" gauge is slightly less in diameter than the "not to go" hole of the "working" gauge; the "inspecting" "to go" hole is a tiny trifle larger than the diameter of the finished shell than is the "to go" hole of the "working" gauge. The accompanying diagram scaled to convenient fractions of an inch will perhaps help to illustrate the meaning of these tolerances. Suppose for instance that the correct finished diameter of our shell is 5-31/32 inches, the tolerances allowed by the Government (_i.e._ the final "inspecting" tolerances) can be represented by the two semicircles and dimensions shown below the centre line, which, as will be seen, are further from the finished dimensions than are the two semicircles and dimensions shown above the centre line, these latter representing the "working" tolerances, the difference between the two sets of figures representing the amount of margin kept up his sleeve by the Inspector by way of control over the machinists using the "working" gauges only. In actual practice of course the fractions of an inch representing these tolerances are infinitely smaller than those shown above for the purpose of illustration only.