A key for a strap is termed a cotter ; and if the name were not used for any other kind of key, the term would be significant; but it is also used for piston-rod keys, crank-pin keys, and keys in the ends of bolts; by such usage the name cotter is more confusing than definite. The better plan would be to apply the term only to those keys which have rows of small holes bored in the small ends for the admission of split-pins. The name cotter would be suited to such keys, because they are neither split-keys nor gibs.

A key intended for a strap is thoroughly welded to allow the pin-holes to be bored into solid metal; and strap-keys that require frequent fixing and unfixing may be made of soft steel. Small strap-keys, being without heads, are quickly and conveniently made by tapering the end of a long bar, and cutting off each key, when reduced to its dimensions, by means of the anvil-chisel and stop, which is placed upon the anvil-measure, as in Fig. 85. When a large number of taper keys are required, the author's rule mentioned in page 8 is useful, in order to ascertain the precise quantity of iron or steel necessary to produce the required length of key.