def check_cols(board: list) -> bool:
    """
    Checks if there are no duplicates in the board's columns.

    >>> check_cols(['**12', '1234', '2481'])
    True
    >>> check_cols(['**12', '1234', '1481'])
    False
    """
    for col in range(len(board)):
        col_nums = set()
        for row in range(len(board)):
            try:
                if isinstance(int(board[row][col]), int):
                    if int(board[row][col]) in col_nums:
                        return False
                    else:
                        col_nums.add(int(board[row][col]))
            except ValueError:
                pass

    return True