Bootstrap. How to add bottom margin for mobile screen only?

Answer 1

Bootstrap 4 allows hidden-sm-up classes, which toggles one object from sm to xl.

Then, you can add a column between each image column, and add this class that will be visible only in mobile devices.

More info: https://v4-alpha.getbootstrap.com/layout/responsive-utilities/

"Available classes"

Sorry my english, :D