Summary

This thing was made with Tinkercad. Edit it online (scale, make hole, height, etc.) at: https://www.tinkercad.com/things/0dQJxF5nfhm

Instructions

Scale and position this solid STL on a flat area of your print raised slightly above the surface, or convert to 'hole' in Tinkercad and sink it into the flat area of your print as a relief STL (see image for example). You're helping to keep printed ABS out of the landfill, so that it can be returned to the recycling stream where it belongs. So thanks!

#9 ABS Symbol