Once the desired path of insertion has been found the position of the cast holder should not be changed. The position of the tip of the clasp is marked at the precise spot where the undercut gauge touches the surface of the tooth in the undercut while the shank remains in contact with the tooth at the height of contour. The graphite rod is then used to delineate the entire survey line (Fig. 45).
The cast is removed from the holder before outlining the clasp form. The clasp is drawn, beginning at the tip and leaving the undercut, towards the survey line. At approximately half the length of the clasp the survey line should be reached. Therefore, the initial half of the clasp, nearest the body of the clasp unit, must function as the upper arm, or shoulder, since it lies above the survey line (Fig. 46).
The clasp arm for lower molars includes the entire arm encircling the tooth from mesio- proximal over the buccal, then distal and ending at the mesio-lingual surface. For upper molars it includes the entire arm encircling the tooth from the mesio-proximal over the palatal, then distal und ending at the mesio-buccal surface (Fig. 47).
The retentive clasp arm for premolars includes the surveyed portion from disto-buccal to mesio-buccal (Fig. 48).
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