Many companies, my employer included, uses spreadsheets on a more or less consistent basis in order to track such things as vacation planning and KPI reporting. For me, as an employee, keeping track of these spreadsheets can, from time to time, be a bit annoying. Much to my surprise, at some point in the past few years, Microsoft added a pin item feature to MS Office.
In order to pin a spreadsheet, document, or presentation, simply hover over the file in question, and a pin will show up on the right. Click the pin and hey presto, the file has been pinned: