Non-encompassing strokes
 

How do you create an object with a stroke that doesn't go all the way around it, a la the “parallel lines” and “quarter arc” objects?

I ask because I’m trying to create a select field/pop-up menu UI element out of a table so it can be easily resizable. I would like to put a stroke around the entire element. I start out by creating the left end cap, but in order for the stroke to appear seamless with the middle portion of the element, I have to create a bezier line that doesn’t extend around the right edge of the cap. I then group the line and the cap. That accurately reproduces the visual effect I want. I do the same for the right end cap. However, when I go to make the table, I find that I cannot include groups in a table. If I ungroup the items and create a table, it naturally places every item in its own cell. If I could create one object that has non-encompassing strokes, like “parallel lines” and “quarter arc,” then I wouldn’t have this issue.

If there’s another way I could do this (without using background images), I’d welcome suggestions. And of course, any help is much appreciated.