I worked as a parcel post distribution clerk in my mis-spent youth, sorting all the parcels inbound to San Francisco. We stood at a conveyor belt facing a wide and deep field of hampers, one for each zip code in the 941 sectional center, plus one for each big mailer, such as catalog companies -- maybe 60 or 70 all told. The game was to read the Zip, then toss the box into the right hamper. None of us were NBA stars, so we missed a lot. No worry, because those mis-tossed boxes would come back from the wrong station the next day, or maybe the day after. If we missed a 30-foot toss entirely, and the box landed on the concrete floor, it stayed there til a mail handler -- the guys who dumped sacks of cartons on to our conveyor -- got around to picking it up. Or not.
My most vivid memory of the conveyor line is a decal of a man kicking a pack of cigarettes, over a cartoon balloon that said KICK THE HABIT. Only somebody had neatly added eyes and whiskers to the pack, changed the cigs to long floppy ears, and changed the the H to an R. KICK THE RABIT.
Then I got promoted to driving the forklift part of the day, mainly because no one else wanted to. Had to get a special license.
Best part of that job was driving back and forth over anything marked FRAGILE. Back and forth, back and forth, cruncha cruncha crunch. Oh Joy! What Cheer!
Long before that I had worked after school in a small department store, mainly in the shipping department. My boss there taught me this rule for packing glassware. Pack it so well that you can kick the package all the way to the Post Office (two blocks away), including bouncing it off curbstones and moving cars, and it will arrive undamaged at the PO. It will then have better than 50% chance of arriving intact at its final destination. And NEVER EVER EVER mark anything FRAGILE. Only later did I find out why, did I become the reason why.
Two days ago at the PO I asked a clerk if they still use the hamper system for inbound parcels. With a

she says, YUP!
* * *
How do I ship now? Valuable knives by Registered Mail, packed to survive nuclear blast. Ordinary knives by Priority Mail, insured for full value. Books by Media Mail. Manuscripts and photos by UPS red label (because I always procrastinate til the last minute). Overseas knives by Fed Ex (I admire the heck out of UPS, but their international service will not take antiques, and they are even worse at paying claims than Allstate).
* * *
Yeah, it is illegal to mail switchblade knives. Same penalty as a letter bomb. And there is no federal parole or probation. Share a cell with the Unabomber!
Also illegal to mail an ad offering a switchblade for sale, or any publication containing an ad offering a switchblade for sale.
Last time I checked, the high school defense "But all the other kids are doing it

" is not recognized in federal courts.
First Amendment? Second Amendment? What you talkin about, punk?
BRL...