An employer shall ensure that every ladder is constructed of sound material and is suitable for the purpose for which it is used, and -
(a) is fitted with non-skid devices at the bottom ends and hooks or similar devices at the upper ends of the stiles which shall ensure the stability of the ladder during normal use; or
(b) is so lashed, held or secured whilst being used as to ensure the stability of the ladder under all conditions and at all times.