code: protected function drawBorderBottom($isCore = false)
  	{
  		$this->geometry->decreaseNesting();
  
  		$crossroads = $isCore ? static::CROSSROADS_DOWN : static::CROSSROADS;
  
  		$this->drawBorder(static::BORDER_SW, $crossroads, static::BORDER_SE);
  	}
docs: Draw the bottom border.
  
  @author	Andrea Marco Sartori
  @param	boolean	$isCore
  @return	void