framework/console/widgets/Table.php
protected function renderSeparator($spanLeft, $spanMid, $spanMidMid, $spanRight)
    {
        $separator = $spanLeft;
        foreach ($this->_columnWidths as $index => $rowSize) {
            if ($index !== 0) {
                $separator .= $spanMid;
            }
            $separator .= str_repeat($spanMidMid, $rowSize);
        }
        $separator .= $spanRight . "\n";
        return $separator;
    }
protected function renderSeparator($spanLeft, $spanMid, $spanMidMid, $spanRight)
    {
        $separator = $spanLeft;
        foreach ($this->_columnWidths as $index => $rowSize) {
            if ($index !== 0) {
                $separator .= $spanMid;
            }
            $separator .= str_repeat($spanMidMid, $rowSize);
        }
        $separator .= $spanRight . "\n";
        return $separator;
    }
Renders separator.

@param string $spanLeft character for left border
@param string $spanMid character for middle border
@param string $spanMidMid character for middle-middle border
@param string $spanRight character for right border
@return string the generated separator row
@see \yii\console\widgets\Table::render()