not sure what to call this, but it's the small bit of standing rigging that counters the upward pull of the staysail; its under the deck in chain locker.
Mine was composed of a turbuckle, swaged eye and a staylock eye. Because it was buried under wet chain and line, the swage fitting (the lowest part) corroded.
I replaced that small bit of 1x19 wire (half the strands were broken, swage was cracked, and the staylock was pitted) with a 12" x 3/8' thick 316 SS flat bar
http://s1278.photobucket.com/user/scherzoja/library/Staysail%20support%20rigging-under%20deck
Anyone with this setup really needs to check it carefully to make sure it is not corroded by all the moisture.