Perhaps you mean a public demonstration by UNION MEMBERS, not just workers. And the purpose is not to inform the general public. Picket lines are formed to signal other unions that the employer has raiosed the ire of a union and suppliers should not cross the picket line, harming the employer.
A Picket is a demonstration by workers for the purpose of publicizing alleged grievances, persuading the public not to do business with the affected company.
picket
picket line
The immediate cause of the Haymarket riot in Chicago in 1886 was a bomb going off at a labor demonstration. Striking workers were asking for an 8 hour day and the public was showing their sympathy for the workers by also taking part in the demonstration.
for Safety and to know what it looks like.
To protect workers
a group gathers to pursue a common purpose.
One purpose of creating the working mens party was to protect the rights of skilled workers.
The purpose of an expository essay is to explain a topic. The essay can be an explanation about a demonstration, lecture, to clarify a process or to instruct a reader on how to do something.
The purpose is for the workers to get better working conditions and pay.
The purpose of the chicano movement was for undocumented workers,students and people to have equal rights and for latinos not to be discriminated
The purpose of the health and safety policy is to ensure that workers have favorable work environment, This is aimed at protecting workers while they are in course of duty.