To restrict access to specific folders for your contacts, navigate to the Lead or Job and select the Files tab.
On the right side of the folder, click the ⋮ button and select Sharing Access to manage options for sharing with your clients, suppliers, or contractors.
Use the tick boxes to grant access to your contractor, supplier, or client, and Save.
💡Remember, this will also share all subfolders and files within the folder.
See this article to set up templated folder structures for different project types.