Content Left Border

I've found a number of classes to which I can add the border to, including .node, .content-middle, and .region-content. However, in order to align the border with the edge of the menu bar, I also need to add a negative margin to the left side of the class as well. As a result, the content of the node is shifted to the left along with the border. What would be the best way to add a border to the left side of the main content without changing the positioning of the text/content within the node?