based on some I've seen,   maybe a big set of vice-grips or Channel-locs and maybe a hammer     
I've got a couple good scopes with "stuck" adjustments too.  I'm assuming the old factory lube has dried out and or previous owners have jammed the threads.   I have been tempted to try to disassemble them and try to clean/free them up; however a very painful experience when I was a kid and disassembled my dads prize WW2 GI souvenir binoculars prevents me from making the attempt.  Eventually I'll have to bite the bullet and send them off for repairs