[Figs. 1474], [1475], [1476], [1477], and [1478] represent the process of testing the alignment of a link with a straight-edge. First to test if the single eye e is in line with the double eye f at the other end, the straight-edge is pressed against the face of e, as in [Fig. 1475], and the distance i is measured. The straight-edge is then applied on the other side of e, as in [Fig. 1476], and the distance h is measured, and it is clear that if distances h and i are equal, then e is in line with the double eye. To test if the double eye f is in line with the single eye e, the straight-edge is pressed against the face of the double eye in the positions shown in [Figs. 1477] and [1478], and when distances j and k measure equal the jaws of the double eye f are in line with those of the single eye e.
Fig. 1479.
Fig. 1480.
Fig. 1481.