thats the one you need to put the spanner on.

it doesn't rotate on that point though, the pivot is inside the housing.
try putting a spanner on pointing up then push it left and right and if that fails try the same but with the spanner pointing down.

if it still doesn't move try something longer for more leaverage.

if it still doesn't move then it must be seized.

i've never had trouble with them though so can't imagine 3 are seized!

Can't help you any further i'm afraid without being there