How do i exclude weekend days in a query ?

I'm using the query below, which works fine, now i want to take it one stpe further and exclude all weekends....

SELECT  a.number,
        a.contact_name,
        a.category,
        b.subcategory,
        a.brief_description,
        a.open_time,
        a.assignment,
        a.status,
        b.problem_status,
        b.ticket_owner
FROM    probsummarym1 a
        INNER JOIN probsummarym3 b ON a.number = b.number
WHERE   datediff(d, open_time, GETDATE()) > 3
        AND b.problem_status <> 'Closed'
ORDER BY a.assignmentStart Free Trial