An inventory is essentially a list of things. . An inventory for your self-storage unit will help you work out what you have and where it is. Your self-storage inventory can be a handwritten list posted on the wall of your unit, a note file on your phone or a spreadsheet complete with serial numbers, purchase dates and values. It all depends on what level of detail you need. . It is useful to make a note of replacement values for your stored items for insurance purposes, and your inventory is a reasonable place to record this information. You may need to supply a basic inventory to your storage company, too.