/How did you decide which includes to include? <BOSL2/gears.scad> obviously, but <BOSL2/std.scad> ? / Because, at the top of BOSL2/gears.scad, it tells me which files to include: ////////////////////////////////////////////////////////////////////////////////////////////// // LibFile: gears.scad // Spur Gears, Bevel Gears, Racks, Worms and Worm Gears. // Originally based on code by Leemon Baird, 2011, Leemon@Leemon.com // Almost completely rewritten for BOSL2 by Revar Desmera, 2017-2021, revarbat@gmail.com // Includes: // include <BOSL2/std.scad> // include <BOSL2/gears.scad> ////////////////////////////////////////////////////////////////////////////////////////////// /And what are the basic rules about folder locations for the library and your fresh scad file please?/ The documentation for OpenSCAD libraries, which explains it much better than I can, is at: https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Libraries Just download the BOSL2 distribution zip, unzip it, move it to your OpenSCAD installation's library folder, and rename it from BOSL2-master to BOSL2. -- Sent from: http://forum.openscad.org/