Our inventory tool (originally developed and kindly provided by Dream2Ticia, whose well-stocked and well-rated store here) makes it easy for you to count all parts of a set in order to check its completeness. It can be used to check any set, whether rented or not, feel free to use it.
If you have an account on the site and are logged in, inventories are saved with no time limit. If you are just a visitor, saved inventories will only be accessible from the current session (lasting 2 weeks by default, only for the current browser and unless using private browsing functions).
Find the documentation for this tool by clicking on this link.