Every project ends with a handover pack. It is the set of documents the builders give to the people who will run the site for the next twenty years. On my first battery project ours filled 31 folders. A year later I visited the control room and found them on a high shelf, still in their plastic wrap.

The operators were not lazy. They had a single sheet taped beside the screen, written by hand by a technician called Malin. Everything they needed in the middle of the night was on that page. Our 31 folders had been written to satisfy a contract, and not to help a person.

Write for the night shift

Now I picture one reader. It is three in the morning, an alarm has gone off, and the person on shift has been on this site for a month. They do not need the design history. They need to know what the alarm means, whether it is safe to wait, and who to call.

So the pack I write today has two layers. The top layer is short and is organised by what can go wrong, not by which contractor supplied what. The lower layer holds the drawings, certificates and test records. It is complete, it is indexed, and most people will never open it. That is fine.

A handover pack is finished when the night shift can use it, not when the contract says so.

Before handover I ask an operator who was not involved in the build to find five answers in the pack while I time them. At Ostrand the first attempt took 40 minutes. We reorganised the top layer, and the second attempt took six.

What sits in the top layer

• One page per alarm that matters: what it means, what to do, who to call.

• A single drawing of the whole site that fits on one sheet.

• How to make the site safe, step by step, with photos of the real switches.

• A list of everything that behaved oddly during commissioning, and what we did about it.

That last item is the one builders like to leave out, because it feels like admitting fault. I think it is the most useful page in the pack. Sites have habits. The people who inherit them deserve to know what they are.