Como converter um cabeçalho de coluna e seu valor em linha no sql?

DECLARE @T TABLE(Col1 INT, Col2 INT, Col3 INT)
INSERT INTO @T
VALUES (1,1,1)

SELECT
    *
FROM
(
    SELECT
        t.Col1,
        t.Col2,
        t.Col3
    FROM
        @T AS t
) AS SourceTable
UNPIVOT
(
    Value FOR Col IN
    (Col1,Col2,Col3)
) AS unpvt

1   Col1
1   Col2
1   Col3