04 Mastiff Rear Wheel Removal

Hello. I decided yesterday was the day to remove my rear wheel to replace a worn tire. I expected to see a solid axle bolt with a nut on one side but found a bolt on each side. I removed the bolts and it appears the spacers are shouldered against the swing arm and protrude into the swing arm so they don't drop out. Only had a spare hour so next I need to find out what am I missing to drop the rear wheel? Anybody point me in the right direction? Thanks.
 
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