A more thorough explanation:

A short-form agreement is a type of contract that is commonly used in labor law. It is usually entered into by a small independent contractor who agrees to be bound by the terms of a collective-bargaining agreement that has been negotiated between a union and a multiemployer bargaining unit.

For example, let's say that a small construction company wants to work on a project that is being overseen by a larger organization. The larger organization has negotiated a collective-bargaining agreement with a union that represents the workers on the project. In order to work on the project, the small construction company would need to sign a short-form agreement that would require them to follow the terms of the collective-bargaining agreement.

Another example of a short-form agreement might be a contract between a freelance writer and a publishing company. The publishing company might have negotiated a collective-bargaining agreement with a writers' union that sets certain standards for pay, working conditions, and other factors. In order to work with the publishing company, the freelance writer would need to sign a short-form agreement that would require them to follow the terms of the collective-bargaining agreement.

Overall, a short-form agreement is a way for small independent contractors to work with larger organizations that have already negotiated collective-bargaining agreements with unions. By signing the agreement, the contractor agrees to follow the same rules and standards that apply to the unionized workers on the project.