The CROSS APPLY and SUBSTRING below should do what you need. Let us know if you need some clarification for getting it into an UPDATE statement.

DECLARE @leading_trailing_chars_to_eliminate varchar(10)

SET @leading_trailing_chars_to_eliminate = CHAR(9) + SPACE(1)

----------------------------------------------------------------------------------------------------

DECLARE @patindex_pattern varchar(20)

SET @patindex_pattern = '%[^' + @leading_trailing_chars_to_eliminate + ']%'

SELECT

'~~' + remarks + '~~' AS [~~remarks_original~~],

'~~' + SUBSTRING(remarks, starting_byte, LEN(remarks) - starting_byte - ending_byte + 2) + '~~' AS [~~remarks_updated~~]

FROM (

SELECT CHAR(9)+CHAR(9)+SPACE(3)+CHAR(9) + 'remarks themselves' + CHAR(9)+SPACE(2)+CHAR(9)+SPACE(1)+CHAR(9) AS remarks

) AS test_data

CROSS APPLY (

SELECT

--find the first not-to-be-eliminated character in the string

PATINDEX(@patindex_pattern, remarks) AS starting_byte,

--find the last not-to-be-eliminated character in the string

PATINDEX(@patindex_pattern, REVERSE(remarks)) AS ending_byte

) AS ca1