How to add triangle above dropdown on bootstrap2?

Question

css

It is necessary to add a triangle above the drop-down menu as in this screenshot.
How to do it?

Answer 1

<div class="arrow-up"></div>

.arrow-up {
  width: 0; 
  height: 0; 
  border-left: 15px solid transparent;
  border-right: 15px solid transparent;
  border-bottom: 15px solid black;
}

eg: jsfiddle.net/p9Dw6/1

Answer 2

.block-class:before {
  width: 0; 
  height: 0; 
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
  border-bottom: 20px solid black;
}

Answer 3

He is there and he is. See if you're doing something wrong.
In general, you can follow the link getbootstrap.com/2.3.2/javascript.html#dropdowns to see how it is implemented in bootstrap, in case you changed something there.