The Form Builder is where you can create most of your custom fillable forms for use in SiteDocs.

However, Follow Up Forms cannot be built there, which is why you also have access to the Flag and Follow Up Form Builder. 

In function, these two pages are very similar. The same Form Items are available, and the building functions are the same with one exception. When you build a Follow Up Form, "Assign to Worker" and "Due Date" are automatically included, no matter what the rest of the Form looks like. These two items are crucial in the function of a Follow Up Form. To learn more about how Follow Up Forms work, click here!

The two items mentioned above look like this in a finished Follow Up Template: