code: protected function applyLockBetween($lft, $rgt) {
      $this->node->newQuery()
        ->where($this->node->getLeftColumnName(), '>=', $lft)
        ->where($this->node->getRightColumnName(), '<=', $rgt)
        ->select($this->node->getKeyName())
        ->lockForUpdate()
        ->get();
    }
docs: Applies a lock to the rows between the supplied index boundaries.
  
  @param   int   $lft
  @param   int   $rgt
  @return  void