SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3 - https://docs.sitefinity.com/label-layout-elements

LabelFormElements.ascx

<div runat="server" class="sf_cols">
  <div runat="server" class="sf_colsOut sf_2cols_1_25" data-placeholder-label="Left Sidebar">
    <div runat="server" class="sf_colsIn sf_2cols_1in_25">
    </div>
  </div>
  <div runat="server" class="sf_colsOut sf_2cols_2_75" data-placeholder-label="Content">
    <div runat="server" class="sf_colsIn sf_2cols_2in_75">
    </div>
  </div>
</div>