It's a (.pen) file for use in processing .plt files with software like buzzsaw apprentice etc.
They might make a .ctb now - not sure.

http://www.signaturecad.com/downloads/Squiggle5UserManual.pdf

blech! those look terrible!!! just draw by hand.

you can make a squiggle in Illustrator as a pattern brush. plot to file as an eps and then change all the lines to your brush.

cris- those are pretty bad indeed. there is a napkin command in autocad that does the same. but it looks equally as ridiculous.

Well I actually like Squiggle and use it for presentations often. The newer versions round-trip the .dwg file which is nice. You open it in Squiggle, apply your custom squiggle settings (of which there are many options to control) save again as a dwg and open back up in Acad for tiles, notes… and print directly out of acad.

Squiggle works really well for printing on Arches and water coloring over. If you f-up your rendering just print another and start painting again.