The old saying goes, “The devil is in the details.”

Except that’s not always true. Sometimes the devil is in the lack of details.

Recently, I loaned a demo portable LED projector to a dealer client for evaluation.

They liked it, but they had one complaint — and it was a big one: They couldn’t figure out how to wirelessly cast from their phone or tablet.

That’s a problem, because the feature is listed right there on the box.

So I apologized for the inconvenience, took the demo unit back and tested it myself at home.

They were right. It was not at all clear how to mirror a phone screen in the device’s menu, nor in the manual or startup guide that comes with the unit.

I did figure it out, eventually. But it took too long. And my dealer was right: The ability to cast from your phone was there all along, but it was in no way obvious or intuitive.

I won’t bore you with all the troubleshooting details. I saved those for the field report I sent to my category manager, who oversees that brand.

This is a concern because if both my dealer and I — industry professionals — struggled to make this work, end users will struggle too. Which means dealers who stock this projector could be dealing with unnecessary tech support calls and returns.

Two things stood out.

First, part of the problem is that when a list of devices on your network appears on your phone, the projector’s default name in the general settings isn’t something obvious like “[Brand] Projector.”

Instead, it’s something obscure with a long string of numbers. When it appears in the list of available devices, it could be anything.

The other issue wasn’t the product itself; it was the manual.

The user guide, like many these days, is three or four pages of pictograms and minimal text, then repeated in Spanish and French.

One extra page — just one — explaining how to cast from a phone over the supported wireless protocol would have solved the issue.

But it’s not there. So I had to figure it out myself.

Most end users don’t have the patience to troubleshoot a feature that’s supposed to work out of the box. You have to show them how to use it.

The first priority in UI design should be to make everything simple and intuitive.

If you can’t do that, the next priority should be to spell out in the documentation exactly what to do.

But that second priority isn’t ideal. If you’re a UI designer, go back to the first point — make everything simple and intuitive — and don’t leave your workstation until you’re finished.

This problem has been building for years. I’ve been in the business long enough to see manuals for electronics go from book-length resources — like the ones that still come with new cars — to brief overviews, sometimes printed on a single sheet of paper.

Poor documentation never solved anything. But it can certainly cause problems.

I’ve debated with friends about whether knowledge really is power. There’s an argument either way.

But when it comes to manuals and documentation, knowledge does give you power.