The short version: most self-custody failures aren't technical. The wallet is sound, the seed is written down, the procedure is correct — and it's all sitting somewhere that doesn't work for the person who'll need it. Correctness and reachability are different properties, and only one of them gets checked.

In September we put straw in the shelter at the back of the garden. In October we re-roofed it, checked the blocks underneath, and got it ready for its second winter. Good shelter. Dry, insulated, raised off the ground, facing away from the wind.

In late October it became obvious that the kittens weren't using it. Not because anything was wrong with it. Because it was forty metres from where they actually live, past an open stretch they won't cross, and a month-old kitten's world is about four metres wide.

So we built another one, badly, out of a styrofoam box with a roof on it, and put it where they already were. They moved in.

The good shelter is still there. It's still the better shelter. It is also, for the animals it was built for, decorative.

I have never found a cleaner illustration of the single most common failure in self-custody.

1. The failure nobody plans for

Think about what people check when they set up a wallet:

Is the seed written correctly? Is the device genuine? Did the restore test work? Is the passphrase right? Is the metal backup fireproof?

All good questions. All about correctness.

Now the questions almost nobody asks:

Can the person who'll need this actually get to it? Do they know it exists? Will they know what to do when they're holding it? Is it somewhere they'd be allowed to go? Would they find it in the state they'll be in when they go looking?

These are about reachability, and a backup that fails on reachability fails completely, no matter how correct it is.

2. What this looks like in practice

The backup in a bank deposit box, in your name only. Correct, durable, secure. Your heirs cannot open it without a court process that takes months, and they can't start that process without knowing it's there.

The seed at your parents' house, 2,000 km away. Fine for burglary. Useless at 11pm when you need to restore because your device died, and worse than useless if the relationship cools or they move.

The instructions written for someone who already understands. "Restore from the seed using the standard derivation path." You know what that means. The person reading it after you're gone has never heard any of those three words in that order.

The brilliant scheme nobody else can execute. Shards in three locations, a passphrase in a fourth, a procedure in your head. Robust against every attacker and against your own family.

The device in a drawer, and no one knows which drawer. The most common one of all. Not hidden — just never mentioned.

In each case the engineering is sound. The thing is simply forty metres from where it's needed, across ground nobody will cross.

3. The test that catches it

Correctness is tested by restoring. Reachability is tested differently, and it's uncomfortable, which is why it isn't done.

Hand the written materials to the actual person and leave the room. Not a walkthrough — hand them the envelope, go out, and let them attempt it with a trivial amount. Whatever they ask you through the door is the gap in your documentation. Write down their questions; those are the instructions you were missing.

Try it yourself from cold, in bad conditions. Not on a calm Sunday with the device in front of you. Late, tired, from the written record alone, with no internet access to look things up. That's the state you'll be in.

Ask who has permission, not just access. A safe your partner isn't named on, a house they can't legally enter, a drawer at an address that stops being yours. Legal reach and physical reach are not the same thing.

Check the distance annually. People move, relationships change, banks close branches. A plan that was reachable in 2023 may not be now, and nothing will tell you.

4. The uncomfortable half

Reachable and secure pull against each other, permanently, and there is no setting that resolves it. Everything you do to make a backup easier for your family to reach makes it easier for a burglar, a coercive relative, or an opportunist. Anyone telling you they've found an arrangement with no trade-off has simply picked a side and not told you which. What you can do is choose deliberately rather than by accident — and most people default to secure, because it feels responsible, and then die having optimised against the wrong threat.

I'd also warn against over-correcting. The answer to "my family couldn't access this" is not to leave the seed on the kitchen table with a note. There's a version of this article's advice that ends with someone's coins in a drawer anyone could open, and that person will have been told they were being practical.

And the honest reason this gets skipped isn't technical. Testing reachability means sitting with someone you love and talking about you being dead or incapacitated. It is genuinely unpleasant and everyone finds a reason to do it later. The whole category of failure persists because of that, not because the problem is hard.

One narrower caution: if you're going to improve one thing after reading this, make it the written instructions, not the storage. Storage failures are rare. Comprehension failures are the norm.

The good shelter is dry, insulated, correctly built, and empty. The kittens are in a styrofoam box, because the box is where they are. 🐾⚡