I'm not sure about the other Scag Mower models, but the Cheetah owners manual calls for removing the small metal plugs on the front of the two front caster wheel housing, and install a zerk for the purpose of greasing, then remove the zerk and replace the two small metal plugs.
The only reason I can see doing this is so the zerks won't be subjected to any material that might tend to break off the zerks while mowing. For me it's a once a year job.
To the rest of you:
Do you follow the manual's instructions, or do you leave the grease zerk in place once the greasing is done...???