Don't use a big hammer
Dennis:Yep, you are supposed to make sure that the zincs are in good contact with the shaft to keep corrosion from building up between the shaft and the zinc, but there is no need to use a real big hammer. Put something against the other side of the zinc, brick, heavy metal object, or something to absorb the shock and just tap it. Zinc is fairly soft so it will not take a real heavy pounding to set it.Good Luck!