A union closed shop is a workplace in which only union workers are allowed and to work and an open shop allows non union workers

Closed shop.

Agency shop.

Open shop.

Union shop.

This question needs to be rewritten. I can think of union terms for "open/closed" shops, but I am not sure this is what you want.

Select a union and ask them for help. Usually there is a card drive (where employees sign up to be union), a vote to certify the union and then contract negotiations.

It's a fairly simple process unless there are multiple unions trying to get in to the same shop.

The agency-shop policy allows both union and nonunion workers to be employed by an organization, but the nonunion employees must pay a union fee equal to union dues.