The tradesperson's three QR codes: van, board, invoice

A plumber's van goes past at thirty miles an hour with an eleven digit number on the side. Somebody wants a plumber. They get seven of the digits.

That is the whole problem with print for trades: the people who need you see your details in the worst possible conditions — moving, at distance, in the rain, up a ladder, three months after the job. Three codes cover the three places that actually happens.

1. The van: a phone code, printed big

A phone code opens the dialler with your number already in it. Nothing to write down, nothing to mistype, no digit lost to a passing lorry.

Two things matter more here than on any other surface.

Print it larger than feels necessary. A van code is read from further away than a business card and often while one of you is moving. The size the generator gives you is the minimum that works at arm's length — a van is not arm's length. If in doubt, double it. Nobody has ever failed to scan a code for being too big.

And print the number next to it. This is the one code type where the fallback is free: a phone number is short enough to sit beside the code in a single line, and it serves everybody who will not scan a thing on principle. Every other type on this site is too long to print as text. This one is not, so do both.

2. The site board: a WhatsApp code

On a board, a hoarding or a sign at the gate, the better code is WhatsApp — for a reason that has nothing to do with fashion.

A photo of the broken thing, sent from where the broken thing is, is worth ten minutes of somebody describing it down a phone line. You can price it properly, you can tell them it is not urgent, and you can do all of it between jobs instead of standing in a loft with a phone under your chin.

It also solves the thing that quietly loses work: you cannot answer calls when you are under a floor. A missed call is a customer who rings the next person on the list. A WhatsApp message waits.

The part most people do not know is that WhatsApp normally makes somebody save you as a contact before they can message you. A code skips that entirely and opens the chat. That is three steps and a decision removed from a stranger standing on a pavement.

3. The invoice: a contact card code

The invoice is the one piece of paper that gets kept. It goes in a drawer, and three months later the boiler makes the noise again and somebody goes looking for it.

A contact card code on the last page puts your name, number and email straight into their phone in one tap — spelled correctly, in the right fields, filed under your actual name rather than an unsaved number they will not recognise when it rings back.

That last part is worth more than it sounds. Being saved as “Dave — heating” instead of an unknown 07 number is the difference between being called first and being called after two other people did not answer.

The same code belongs on the job sheet and the service sticker on the boiler itself. Anywhere the next person to have this problem will be standing.

The fourth one, when you are ready

Trades live on being recommended, and increasingly on being searchable. A Google review code on the invoice, next to the contact one, asks for the review at the only moment it is easy to ask: the job is done and it went well.

Show it to everybody, every time. Deciding who gets shown the code is both against Google's rules and the thing that makes the whole exercise feel grubby. Ask all of them and let the average be the average.

Start with the van

If you do one thing, do the van, and make it bigger than you think. It is the only advertising you already pay for and are currently getting seven digits of value out of.

The codes are free and static — the details sit inside the code rather than on a page somebody keeps running — so there is no account, no monthly fee, and nothing that stops working next year. Print them on the next batch of whatever you were printing anyway.