Kinds of Bargaining arrangements
Basically there are three kinds of bargaining arrangements, namely:
In an open shop a union represents its members, but does not have an exclusive bargaining jurisdiction for all workers of one kind. Membership in the unions is not condition of getting or keeping a job.
In this arrangement only union members may be employed and the union controls membership however it sees fit.
The employer may hire anyone he chooses but every employee must join the union within a specified period.