Why are feeler gauges a bad idea and in general just wooly thinking?

When setting the z offset what's bad about using feeler gauges?

Answer:

Feeler gauges are a horrible idea for several reasons:

metal feeler gauges thermally change dimension
dangerous to use on hot plate
damage bedplate
sets to arbitrary height

The gcode z offset needs set to achieve an affect, a squish, on the filament which must be observed rather than set to some arbitrary height we measure.

Read more about understanding the gcode z offset