When a group of employees strike against their own employer--the primary employer-their purpose usually is to disrupt his operations in the hope that economic pressure will persuade or coerce him to meet their demands. They may picket the primary employer's premises in order to publicize the strike or to try to persuade fellow employees to join it; and even if the picketing induces third persons not to deal with the primary, the employees' activity constitutes protected primary picketing. If the goal of the striking employees is in fact to publicize the strike and to persuade their co-workers, they will naturally picket where they will reach the public or those employees. If, however, the striking employees should decide that such tactics do not sufficiently influence their employer, they might elect to picket the premises of a secondary employer who deals with the primary employer, in an attempt to persuade the secondary's employees to refuse to handle the primary's product. If those secondary employees cooperate with the striking union, the secondary employer may be compelled either to pressure the primary into accepting the union's demands or to cease doing business with the primary. This prototype of the secondary boycott is prohibited by section 8(b)(4)(ii)(B), and it demonstrates that the usual purpose and effect of picketing on secondary premises is to disturb the operations of a party not directly involved in the dispute beforehand.

The essence of the distinction between primary and secondary picketing is normally whether the business operations of the primary employer take place at the site picketed. This issue may be complicated, however, by the possibility that elements of both primary and secondary operations may be present at one location. The Auburndale case involves such a situation, because the primary employer's product is located on the picketed premises, which are owned by a secondary employer.