[WrtCdEvrydy]

If you're into 3D Printing, feeler gauges are also a great way to level your bed... move the extruder 0.04 above the bed at four points, stick your 0.04 feeler under it and adjust the springs until it touches the feeler. Voila, one perfectly leveled 3D printer bed.

[serf]

that's a weird in-between two more popular ways of doing it.

The non-precise way you've already heard about, sheet of paper, check for dragging.

The better (more precise) way, is using a magnetic base micrometer attached to your extruder head. You can then watch the bed run-out in real time; if your 3d printer supports many configurable sections across the bed ( I know Prusa style cartesian units mostly all support quadrants) you can record the run out everywhere across the plane without any more physical work than watching the gauge and recording the results.

P.S. be careful using both the micrometer and the feeler gauges on a 3d printer bed. Most work plates now-a-days are using PEI coatings that'll scrape off easily with metal-on-metal contact.

[WrtCdEvrydy]

> using PEI coatings that'll scrape off easily with metal-on-metal contact.

Yeah, you're correct, it's a glass bed so I use it to do the 4 corners (every few months) and then use a BL touch to do a 3x3 grid on top of it.

[jrockway]

Most people use a sheet of paper for this. I wouldn't use it to check the tolerances of an airplane part, but it gets you 99% of the way there.

[WrtCdEvrydy]

I like the sheet of paper method, but I have gotten a lot more use out of a $0.15 feeler gauge and I get consistently better prints... but I don't have the tools to scientifically quantify it so it could be placebo.