We’ve all heard “measure twice, cut once”, right? But if you don’t mark the measurement, you might as well not bother measuring at all.

To mark wood, you could use chalk, or a pencil. But those don’t work very well on metal. You need something more precise. You need a scriber, and layout fluid.

Image of layout fluid, two scribers, dividers and hermaphrodite or oddleg calipers.
From left: Layout fluid, a scriber, another scriber, dividers, and hermaphrodite dividers.

Scribes required (Pharisees optional)

You certainly could find simple ways to mark metal. A sharpie will work just fine, for example. But it leaves a pretty wide line, so the marks lack precision.

I drew a line with a permanent marker. It’s about 1/16″ wide. Plenty visible, but not very precise.

If you draw a sharp point across the metal, you’ll make a very precise line, but it’s hard to see.

It actually shows up better in the picture than it does to my eyes. But it still isn’t great.

But if you first cover the metal with layout fluid, like this…

It still isn’t quite dry in this picture, particularly in the lower right-hand corner where I got it a little thick.

… and then scribe the line, like this…

The dye still wasn’t dry when I sat the square on it.

… the line shows up really well!

So what is layout fluid?

Layout fluid is a mix of shellac, denatured alcohol, and a dye to provide the color. Dykem is the best-known brand, but I have used other brands too.

What I like about layout fluid is that it dries fairly fast, and shows marks really well. Since it gives such great color contrast to the metal, even very faint marks show up well. That means that I can make a mark in the dye without marring the finish of the piece I am working on.

I also appreciate that the dye sticks really well to the metal. I have bits in my scrap bin that were marked a decade ago, and the dye is still there.

When the time comes to remove the dye, a little lacquer thinner takes it right off. Denatured alcohol will too, though it takes a little more elbow grease.

Just about everything I make in the machine shop gets slathered in layout dye at some point along its journey from “chunk of metal” to “smaller chunk of metal”. It’s a truly vital tool, and one of my favorites.