title: When to use which material design svg folder
body: <p>In the <a href="https://github.com/google/material-design-icons" rel="nofollow noreferrer">material design icons github repo</a>, each svg folder has two subfolders, <a href="https://github.com/google/material-design-icons/tree/master/action/svg/design" rel="nofollow noreferrer">design</a> and <a href="https://github.com/google/material-design-icons/tree/master/action/svg/production" rel="nofollow noreferrer">production</a>. They have the same size (shown by <code>du -s</code>), but a <code>diff</code> shows differing content. (EDIT: <code>du</code> only shows block size, actual sizes are different as of the comment).</p>
  
  <p>Which folder is for which purpose? Especially: which folder is intended for combining icons?</p>