A DIY metal backup is cheap, private and stronger than many commercial options. This intermediate how-to is part of our metal seed phrase backups guide. Do read paper vs metal first, to check that it is right for you.

What you need

  • Stainless steel: 304 or 316 grade, in plates or thick washers, at least 2 mm thick if you can.
  • Letter punch set, with hardened steel punches, 3 mm or larger.
  • Heavy hammer, about 1 kg.
  • Solid surface: a metal block or a thick anvil on a concrete floor.
  • Eye protection and gloves.
  • Scrap metal for practice.
  • Clamp or vise, to stop the plate moving.

Buy locally with cash if you value privacy.

Step 1: Practice first

Use made-up words on scrap metal. Do not practice with real words, because you would then have to destroy the scrap. Practice until your letters are deep and clear. Stainless steel is hard, and takes more force than you might expect.

Step 2: Set up in private

Follow the same privacy rules as in writing down your phrase. No cameras, no phones, and no helpers.

Step 3: Stamp each word

  1. Stamp the word number first, from 1 to 24.
  2. Stamp at least the first four letters, as explained in why four letters are enough.
  3. Keep your letters upright and well spaced.
  4. Hit each punch once, firmly, to avoid a double image.
  5. Mark the orientation of the plate, so that the letters cannot be misread.

Watch for letters that could be confused, such as O and Q, or I and L. Stamp a clear line through the plate between words, if that helps.

Step 4: Check every word

Compare the plate against your phrase, letter by letter. If you make a mistake, do not try to fix it. Start again on a new plate, and destroy the failed one.

Step 5: Test and store

  • Confirm your backup with a device check, reading from the steel, not from paper.
  • Store it away from your wallet. See where to store a seed phrase.
  • Protect plates from being read at a glance, with a sealed tamper-evident bag.

Dispose of waste carefully

Practice pieces with no real words are harmless. Failed plates with real words should be ground off or destroyed thoroughly. Do not put them in your household rubbish.