Handbook EL-312 - Employment and Placement - Contents 583 Security Investigations 583.1 Nonsensitive Positions The Postal Service selects and retains only those qualified individuals whose employment is con..." /> Handbook EL-312 - Employment and Placement - Contents 583 Security Investigations 583.1 Nonsensitive Positions The Postal Service selects and retains only those qualified individuals whose employment is con..." />