I am working on a 1986 F350 with a dual rear end and I need to remove the drums for inspection.

I have the axil removed and I'm looking at the nut holding the bearings in and it is rounded (not a hex nut) and flat with 4 square holes in it. Any suggestions on what tool I would use to get this spindle nut off with?

Any steps that I should know about before attempting to spin the nut after I get the tool?

Thanks for any replies I get.