How to send keys by mail

How to send keys by mail

KeysDuplicated is a convenient way to send key copies to friends coming to visit for a few days. AirBNB hosts like to use us to mail keys to their guests.

If you already have a key copy, here’s another cheap and reliable way to mail keys through the US Postal Service: paste the keys on a thin piece of plastic and mail it in a letter envelope with a $0.66 stamp. We mail hundreds of keys this way every day.

To mail keys cheaply, stick them on a plastic sheet, and slip them in a letter envelope.

If you don’t have a sheet of plastic handy, cut out a small sheet from some plastic packaging (the first few keys we sent out like this, I used the packaging from a box of spinach).

This is much cheaper than the more common way of mailing keys in padded envelopes. Those envelopes can cost about $2 and posting them costs another $2.

It’s tempting to mail key without the plastic backing. Resist that temptation. An unprotected key will probably rip through the envelope as it goes through the USPS’s sorting machines.

The Postal Service’s machines munge envelopes. Avoid the temptation to mail keys without the backing sheet. Also, tape the key securely to the backing sheet.

The Backing Sheet Backstory

We experimented with other mailers before we discovered backing sheets. Here’s an early prototype, which we called the Key Kozie.

I have a soft spot for this key mailer, but it ended up not working reliably.

Adorable as it was, the key could still rip through the envelope.

We also tried laser-cutting a key-shaped pattern from a piece of cardboard, and stuffed the key inside the cut-outs. But the envelopes were so thick and rigid that the post office started charging us parcel fees.

Cardboard cutouts made for reliable mailers, but postage wasn’t affordable.

Curiosities in the Postal Service’s Regulations

Somewhere along the way, I noticed this provision in the Post Office’s guidelines:

Additional Criteria for First-Class Mail Nonmachinable Letters

Letter-size pieces (except cards) that meet one or more of the nonmachinable characteristics in 2.1 are subject to the nonmachinable surcharge (see 233.1.4). All letter-size pieces over 3.5 ounces are prepared as letters and charged the flat-size prices. An envelope weighing no more than one ounce with one enclosed standard optical disc no larger than 12 centimeters in diameter, that is mailed to or from a subscriber as part of a round-trip mailing under 233.2.8 and 505.1.0 (or 507.1.0), is not subject to the nonmachinable surcharge.

In other words, as long as you do exactly what Netflix does, you get discounted postage. The USPS guidelines are peppered with Netflix Exceptions like this. That seemed unfair to me. So we started cutting key shapes out of DVDs and mailed DVDs stuffed with keys. Postage was cheap, and the mailers worked reliably. But DVDs aren’t cheap, and by that time, the postmaster knew us well and she was pretty sure we weren’t in the subscription DVD business.

One last curiosity: If you tag a key with an address and drop it in the mailbox, the US Post will deliver it, and charge the recipient:

Keys and Identification Devices

Keys and identification devices (such as identification cards and uncoveredidentification tags) that weigh 13 ounces or less are returned at the applicable single-piece First-Class Mail parcel price plus the fee. Keys and identification devices that weigh more than 13 ounces but not more than 1 pound are returned at the 1-pound Priority Mail price plus the fee. Keys and identification devices weighing more than 1 pound but not more than 2 pounds are mailed at the 2-pound Priority Mail price for zone 4 plus the fee. The key or identification device must bear, contain, or have securely attached the name and complete address of a person, organization, or concern, with instructions to return the key or identification device to that address and a statement guaranteeing payment of postage due on delivery.

This provision presumably exists to encourage folks to return lost keys and security badges to their owners. It’s bad karma to take advantage of it.


The backing sheet strategy works well for us today, and has been imitated by other companies that mail key copies. Try it next time you mail keys.

When we first started, I spent a lot time writing hand-written notes, to pre-emptively apologize for any keys that might fail.