If you've got an item on a project that you are Subrenting from another vendor, you can quickly mark this item as a Subrental from Fulfillment.
First, click the Fulfillment Tab on your project.
Next, find the item you'd like to mark as a Subrental.
Then, click the three dots next to the item and click 'Mark as Subrental'.
Pro Tip: You can add where you're subrenting it from to help you remember those details!