I don't know if this applies to N-400 but I never thought that ACCO fasteners were needed, advisable. In my case I didn't even staple anything. Anyway, this is the text:
"Use paperclips when attaching supporting personal documents to forms (do NOT use “ACCO” fasteners; staples are acceptable when attaching fees)."
from:
http://www.uscis.gov/portal/site/us...nnel=fe529c7755cb9010VgnVCM10000045f3d6a1RCRD
I am posting this, because there were older/earlier posts advising to use this kind of fastener to assemble the application
My 2 cents
"Use paperclips when attaching supporting personal documents to forms (do NOT use “ACCO” fasteners; staples are acceptable when attaching fees)."
from:
http://www.uscis.gov/portal/site/us...nnel=fe529c7755cb9010VgnVCM10000045f3d6a1RCRD
I am posting this, because there were older/earlier posts advising to use this kind of fastener to assemble the application
My 2 cents