Originally Posted by PorFin
Both -- you can drain the water from a closed seacock through the hole; or if you insert a zerk fitting, inject grease into the seacock.
Spartan for example specifically advises against this. Those screws in Spartans are specially made of the same alloy, 85-5-5-5 bronze as the rest of the seacock. There is no such animal as an 85-5-5-5 bronze grease zerk thus installing one introduces dissimilar metals into the equation... They also strongly advise against using that screw for bonding. They are drain plugs for intended winterizing..