Remove only leading or trailing carriage returns

Find the first character that is not CHAR(13) or CHAR(10) and subtract its position from the string’s length.

LTRIM()

SELECT RIGHT(@MyString,LEN(@MyString)-PATINDEX('%[^'+CHAR(13)+CHAR(10)+']%',@MyString)+1)

RTRIM()

SELECT LEFT(@MyString,LEN(@MyString)-PATINDEX('%[^'+CHAR(13)+CHAR(10)+']%',REVERSE(@MyString))+1)