From Willy: Define a standard for helper parts

[Eugen]

Design:

• No edges on 2D helpers as for stickers
  
• Edges on 2D helpers as for parts
  
• Edges Yes/No on 2D helpers - leave the final decision to the author
  
• Edges on 3D helpers
  

Dimensions:

Numbers and letters should fit into a x-z grid of a:

• 20 x 20 LDU
  
• 40 x 40 LDU
  

Small addition, as there is the first "Helpers 2D ..." part to test: https://library.ldraw.org/tracker/37573

I would recommend to add a note that if the "Helpers 2D ..." part is designed to be laid on the flat part (on top or on its side, as many rulers) there should be an offset added for helpers' edges/faces from the base plane set to something like "0.1 LDU" (this is minimal value to input manual transformation in LeoCAD), so when helper would be snapped to the part top/side there would be no Z-fighting between faces.

Here are screenshots of LeoCAD with actual "parts/helpers/helper2druler100ldu.dat" (for each case with show "Edge Lines" turned ON and OFF).

With no offset (as it is in latest revision of https://library.ldraw.org/tracker/37573)

       

With "0.1 LDU" offset: