How to add a vertical blank space in bootstrap?

I am now using bootstrap framework for my web design. It really helps me a lot in front-end design. There are so many useful components, but if I didn't know about them, it'd take me lots of time to trying to do it myself or digging for it. So, I think it's good for me to write down what I have learned and found useful, even though a very simple tiny thing.

I was just looking for how to do this: add a vertical blank space.

I usually just use <br/> or sometimes <p>&nsbp;</p>

I am sure there's a simpler and better way to do so. I searched for it, and I decided to use this:

<div class="help-block"></div>