An automatic centre punch is included which creates a dent in the sheet. It's simple and safe to use. All you do is position it in the centre of the square you want to mark, making sure it is perpendicular to the sheet so it doesn't slip. Then press firmly down on the punch and it will fire the hardened tip into the steel sheet.
The grid is physically etched into the steel, not just a surface mark. This means it will always be there.
The BIP39 word list comprises of 2048 words between three and eight letters long. The way the phrases are designed, the first four letters of each word are enough to uniquely identify it. For example, if the word is “calm” there is no “calmly” on the list. Or if it’s “combine” there is no “comb”.
This means you only need to store the first 4 letters of your phrases, hence why the sheet is only marked with four sub columns per phrase. In the event you need to use this sheet to recover your wallet, you can search for “BIP39” (or use this link) and use this to cross reference these four letters to find the full phrase, or confirm it is a four letter phrase.
If you have three letter phrases, mark the three letters and leave the fourth sub column blank.
The list is accessible here: https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt
Any device connected to the internet is a risk of being compromised. The phrases must be created and stored offline.
Even if you just save the file on a USB and then unplug your USB, you can't guarantee that your phrases are compromised.
Also electronics are fragile to the elements, stainless steel isn't.
Stainless steel offers a great combination of protection from the elements, whilst being tough and durable without costing as much as more exotic metals.
Grade 316 was specifically chosen as it offers more protection against corrosion than lower grades whilst maintaining a melting point of around 1400°C.
For reference, standard house fires are estimated to get to temperatures around 815°C.
1x Etched stainless steel sheet (marked 1-12 front and 13-24 back)
1x Automatic centre punch
Attenuo is a UK owned small business. We are working with UK ISO accredited manufacturers & supply chain to ensure the quality of the product is the best it can be.