The OT describes his situation as:

Renting a pneumatic nailer is not really practical,
since my fence boards get knocked down periodically when baseball
season starts at my neighbors house. And hamering is a problem because
this is a very old fence and using a hamer will just as likely knock
the fence down instead of repairing it.


since the requirement is occasional repair, I suggest using a
drill/driver battery powered & large head deck screws coarse thread.

cheers
Bob