I will rule the world!

How to use it?

LeoCAD does not recognize this part and search in parts list show nothing (maybe its LeoCAD issue due to "|" symbol in the part name).

Also, this part should has some !KEYWORDS ("Helpers, Ruler, LDU", etc.) and !CATEGORY ("Helpers"?).

Added category. Keywords already covered by description.

"Added category.",— I see no any categories in its latest DAT-file.

What about setting all colors in it to "Main (16)" color, so it would be usable on dark background and in other colors too?

Helpers are still a bit experimental on the PT software. We submitted this one during our meeting in Billund to test things out but I haven't gotten back to fixing some of the shortcomings we discovered.

Added category, changed color

PT is still stripping the category. I actually don't think it needs a category since the part type is "Helper".

Maybe indeed it would be more consistent if the numbers were drawn with edge lines, or the graduations be made from very thin quads?

"I actually don't think it needs a category since the part type is "Helper",— I suppose there should be at least "!CATEGORY Measuring Instruments" (aka "Instrumentation") added.

As the new version of this part now has "graduations made from very thin quads" it is bit glitcy looking in LeoCAD, and as its faces coplanar to flat faces of parts (e.g., if place ruler ontop of flat tile) there Z-fighting — to avoid this, I propose for all the faces in ruler part add a small offset (<=2 LDU) from the origin plane in the front direction (according to label text front side).

"Maybe indeed it would be more consistent if the numbers were drawn with edge lines [too]",— I double this, but proposingnfull edge variants of this ruler to be made as two separate subset parts: 1st - for all black edges, 2nd - for all white edges (both with "_" symbol prefix character, as edges colors are not switchable, at least in LeoCAD). Also, all the edges should has small offset from origin plane, same as described above for all faces variant.

So, in a result there would be 3 rulers: main - all faces with adjustable colour; subset 1 - all edges with black colour; subset 2 - all adges with white colour.

Lets table this discussion for now. Helpers aren't ready to be released to the library as the software isn't ready and there's still some discussion that's better suited for the forums.

OK, moved discussion: https://forums.ldraw.org/thread-24904-post-55215.html#pid55215

But should not be this part, as well as other helpers, has "0 |Helper ..." in the description? (i.e., without spaces between "|" and "Helper", same as "~", "=", "_")

The LDConfig makes sure that a black colored ruler will get white edges and vice versa.