Rights aren't about need. They are about choice. Without choice, there is no right. I choose to carry a pocket knife.It gets to the point when people just need to deal with it , you don't need a knife on you 24/7 , you can go on and on about your rights and crap but really not a big deal if you need to leave it in a car for 5 minutes
As to the subject at hand --- I mailed a knife today from a post office near my work. Walked in with my little box of mailing supplies. At one of the counters I wrapped the knife in bubble wrap and taped it. Packed the knife in a small flat rate priority box with more bubble wrap. After addressing the box I taped the box with clear packing tape. Used my knife for all the cutting of bubble wrap and tape. When knife wasn't in hand, it sat open on the counter in front of me. No one, customers or postal employees, even batted an eyelash. Why should they? The public entrance to the Post Office wasn't posted either.