Can you get a compressed air tool for fencing staples or U Nails?

I've got a compressor and living on a farm need to do allot of fencing. I would like to know if any company produces a gun to fit a compressor which will hit large fencing staples or U nails into wooden post. Any answers would be very much appreciated thank you.|||Check Porter Cable, they make a crown stapler. That may work for you.|||They sell air operated staplers, but not sure what sizes can be used. You may want to look at the type roofers are now using for stapling roofing shingles.|||You may try making an attachment to an air chisel.