Utilities begin with a single dash and contain only one CSS property. New ones should not be added unless absolutely necessary. A list of all the available utilities is under sass/components/_helpers.scss

.-fl-l  { float: left !important; }
.-fl-r  { float: right !important; }
.-ta-l  { text-align: left !important; }
.-ta-r  { text-align: right !important; }
.-ta-c  { text-align: center !important; }
.-ta-j  { text-align: justify !important; }

.-hide  { display: none; }
.-nwrap { white-space: nowrap; }
.-ovf   { overflow: hidden; }
.-clf   { @include clearfix; }
.-clr   { clear: both; }

.-f-700 { font-weight: 700; }
.-f-i   { font-style: italic; }
.-mt-0  { margin-top: 0 !important; }
.-mb-0  { margin-bottom: 0 !important; }
.-mt-1  { margin-top: $baseline !important; }
.-mb-1  { margin-bottom: $baseline !important; }