How the marks are made

Engraved markings are the more trustworthy of the two: they cannot wear off, and they are usually cut by the same machine that sizes the rule. A ruler's scale is either printed onto the surface with ink, or engraved - cut or etched directly into the material. Most plastic and wooden rulers are printed; most steel machinist's rules are engraved.

Two failure modes for printed marks

Printed ink wears with handling, and on a ruler used often, the marks nearest the end you press hardest fade first - which is unfortunate, since the zero end is exactly where a bone-pressed reading needs a clear mark. Printing can also be slightly off scale to begin with, since the printing process is a separate step from cutting the ruler blank, and the two are not always aligned to the same tolerance. How far off is allowed depends on the accuracy class, not the marking method: the EU's Measuring Instruments Directive (2014/32/EU, Annex VI) caps the error of a single interval up to 1 mm at 0.1, 0.2 or 0.3 mm for classes I, II and III, and a class mark on the rule tells you which promise was made. Neither failure is obvious by eye until the marks are compared against a known reference length, like a bank card's 85.6 mm edge.

Why engraved marks avoid both

An engraved mark is cut into the material itself, so it cannot wear off with handling the way ink can - short of the ruler's surface itself abrading away, which takes far longer. Engraving is also typically done by the same machine that cuts the ruler to length, on a steel rule, which tends to keep the scale and the physical edge in closer agreement than a separate printing step does.

A middle option

Some rules use etched rather than fully engraved marks - a shallower cut, often filled with black paint or oxide to improve contrast without relying on surface ink alone. This holds up better than pure printing, since the etch itself survives even if the fill wears from the surface over years of handling, while keeping most of the readability of a printed scale. It is a reasonable middle ground if pure engraving proves too hard to read for your eyes or your lighting.

The trade-off

Engraved rules cost about the same as a decent printed one and are common as machinist's steel rules, though less common as the disposable-feeling plastic rulers found in a school kit. The main cost is not price but contrast: an engraved mark on unpolished steel can be harder to read at a glance than crisp black ink on white plastic, particularly in poor light, so there is a genuine legibility trade against the durability gain.

Where the choice matters and where it does not

This is entirely about the length instrument - a rigid ruler used bone-pressed - and has no bearing on a different kind of number. It says nothing about a judgement from Rate Cock, a human reviewer's opinion on Rate Penis, a photo score from Penis Rater, or an AI estimate from an image - none of those read a physical scale, engraved or printed.

If a ruler sees regular use, engraved marks are worth the slightly worse legibility for the marks that never wear off.