A subcontractor can be appointed to a main contractor in several ways, including through a nomination, naming or domestic subcontracting process.

1. Nominated subcontractors: In this process, the main contractor is responsible for identifying and selecting the subcontractors that will be used on the project. The main contractor will typically have a list of pre-approved subcontractors that they have worked with in the past, and they will choose from this list to appoint the subcontractors for the project.
2. Named subcontractors: In this process, the main contractor is required to use specific subcontractors that have been specified in the contract. This may be because the subcontractors have specific qualifications or certifications that are required for the project, or because they have a unique or proprietary product or service that is needed for the project.
3. Domestic subcontractors: This is one that is selected, procured and awarded packages of work by the main contractor, solely at the discretion of the contractor.

In all cases, main contractor is responsible for ensuring that the subcontractors they appoint have the necessary qualifications, insurance, and licenses to perform the work. They are also responsible for managing the subcontractors, ensuring that the work is completed on time, and that it meets the required quality and safety standards.

It’s worth noting that the main contractor is also responsible for ensuring that the subcontractors are paid promptly and that the payments are being made as per the agreement.