This kind is used for a clearfix. We use microclearfix, so by default we have clearing elements both at the top and at the bottom.
By default the block is cleared using pseudos, if you'll want to have the clearfix at another element, you could override its selector using
kind: clear (-after '& > .clearfix')
Clearfix from one side
If you need to use clearfix only at one side, you need to disable it from another by overriding
kind: clear (-before '') kind: clear (-after '')