lib/spreadsheet/worksheet.rb
def merge_cells start_row, start_col, end_row, end_col
      # FIXME enlarge or dup check
      @merged_cells.push [start_row, end_row, start_col, end_col]
    end
def merge_cells start_row, start_col, end_row, end_col
      # FIXME enlarge or dup check
      @merged_cells.push [start_row, end_row, start_col, end_col]
    end
Merges multiple cells into one.