Borders
border
border-top
border-right
border-bottom
border-left
Responsive Borders
For responsive borders use
border-(screen)
border-(side)-(screen)
The (side) values are
top
right
bottom
left
The (screen) values are
screen-xs
screen-sm
screen-md
screen-ml
screen-lg
Examples:
border-screen-xs
border-top-screen-sm
border-right-screen-md
border-bottom-screen-ml
border-left-screen-lg