Illustrator - stroke doesn't connect / brush pattern

Question

so I'm having problems figuring out a stroke issue. Below is an image of what I am referring to.

Essentially, I want to create a brush that I can use on strokes so that no matter the shape, when I use it, I have 3 horizontal lines applied as the stroke.

At the moment, if I use the pattern brush, the outer corners are all over the place. If I use the art brush, the ends do not connect.

What can I do?

Answer 1

I would simply use a Graphic Style which has 3 strokes of varying offsets.

The graphic style will always follow the shape outline without any additional editing.

If you must use a brush, the Pattern Brush is the best option if you want the ends to join. However, you need to set the corners properly:

Corner options only available in Illustrator CC+. For legacy versions, you'd need to manually create your corners.

Be aware, with the pattern brush, the joints may "break" if art is too small. So you'll have to adjust the size of the brush.

Answer 2

you have two choices using brushes.

1. using the pattern brush, and to create corners you have to define the shape of the corners in the pattern brush. please follow this link how to do a pattern brush
2. but if you want to use the art brush or even the pattern brush, you have to add an anchor point between the last anchor that have the problem and the one before it and break it, so the beginning of the brush and its end start and end from that new anchor.

by the way if you give a very little roundness to the corners, this will solve your problem.