shown the slot starts approximately 0 2 inches from the tongue 39 s open end and running approximately 2 2 inches toward its closed end referring again to fig1 5 after the spring arm pin 19 passes through the spring arm 13 and the hole in the primary linkage 17 it passes through the tongue hole 22 attaching the spring arm 14 to the tongue 20 after the driver arm pin 18 passes through the driver arm it passes through the longitudinal tongue slot 23 and then into the primary link 17 the driver arm pin 18 in not fixed in one location in the slot 23 but slides within it a secondary link 26 is also mounted on the driver arm pin 18 between the tongue 20 and the driver arm 13 at a second predetermined temperature 180 u00b0 c that is higher than the first predetermined temperature the secondary link separates many commercially available links can be used with the preferred link being a model a or b fusible link provided by elsie manufacturing company the end of the secondary link 26 opposite the driver pin 18 rests against the outside surface of the tongue 39 s closed end 21 the same end of the secondary link 26 has a hole 26 a that mates with the spring arm pin 19 to reopen the blade 11 after the primary link 17 has separated the spring arm pin 19 is shown in fig6 when installed the head 60 rests against the surface of the spring arm 14 the pin 19 has two axial slots 61 and 62 for holding retaining washers such that the tongue 20 is held between the washers a bias spring 63 is mounted on the pin 19 between the tongue 20 and.