[2013-08-13] Visio 2013 features built-in support for double-lined shapes. See this post.
Visio shapes typically have a single line around the edge (or no line at all), but sometimes you want to create a line with *two* edges.
Single Line:

Double lines:

Typically someone will try to do this by drawing two shapes. With one shape whose sole purpose is to draw the extra line. This technique has a couple of disadvantages:
On the other hand, it is apparently the only solution available.
Except that it isn’t. It’s entirely possible to create a single shape with two lines in Visio. It just isn’t obvious how. The solution is to create your own Line Pattern.
So for example in the list of Line Patterns, you’ll see a custom one:

Although I provide the basic instructions at the bottom of the blog post, there are some nuances that are much more easily grasped by watching the screencast below.
