.float-start, .float-end and .float-none (responsive, as in .float-md-end) replace Bootstrap 4 2,007 's .float-left and .float-right. A parent holding only floats collapses to zero height; .clearfix on the parent adds an ::after block with clear: both that stretches it around them. Floats are ignored on flex items, so use them only to wrap text around an image.