if the metal shield/cage you are refering to, is the same shape as the nut(hexagonal),then it stays in place & you need to find a socket to fit over it to undo the entire hub nut/cage etc. Inside the cage there is normally about 3 nuts, & the cage acts like a self locking assembly. Do not try to break it off,or you will have to buy a new one.
jim
June 2010
it needs tapping off with screwdriver and hammer before undoing nut
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