Bootstrap 3
Here is a working left sidebar example:
http://bootply.com/90936 (similar to the Bootstrap docs)
The trick is using the affix component along with some CSS to position it:
#sidebar.affix-top {
position: static;
margin-top:30px;
width:228px;
}
#sidebar.affix {
position: fixed;
top:70px;
width:228px;
}
EDIT- Another example with footer and affix-bottom
Bootstrap 4
The Affix component has been removed in Bootstrap 4, so to create a sticky sidebar, you can use a 3rd party Affix plugin like this Bootstrap 4 sticky sidebar example, or use the sticky-top class is explained in this answer.
Related: Create a responsive navbar sidebar "drawer" in Bootstrap 4?