Snap nearby points across two or more paths to their average coordinates. This extension can be used to help interlock adjacent shapes like pieces of a jigsaw puzzle.
A tutorial for beginners, teaching how to use clones to draw unique snowflakes, which are perfectly symmetrical. The tutorial is copyrighted, but the snowflake image (sf1.png) is CC-BY-NC-SA. https://forum.inkscapecommunity.com/index.php?action=articles;sa=view;article=27
Snapping since Inkscape 0.91 explained.