I wasn't familiar with the term "neatline" until I read this page from the new book Map Art Lab: 52 Exciting Art Explorations in Mapmaking, Imagination, and Travel. A neatline is a border commonly drawn around the extent of a map to enclose it and all its decorative pieces and parts, keeping all the information pertaining to that map in one "neat" box. The other cool feature is if one side is missing you know part of your map is missing!
Click on this page from Map Art Lab to enlarge and read how to make a striped neatline and some ideas on other materials and ways to make neatlines for your maps and other mixed-media art.
More about the new Quarry craft book:
Travel through the exciting world of cartography with Map Lab. This fun and creative book features 52 map-related activities set into weekly exercises, beginning with legends and lines, moving through types and styles, and then creating personalized maps that allow you to journey to new worlds.
Everyone loves maps. And what’s not to love? They are beautiful and fascinating, they teach you things, they show you where you are, places you long to go, and places you dare to imagine.