Single rooms are available through general lottery (they are not eligible to be squatted). Less than a third of the students on campus live in a single room and only about half of those are on upper-campus. Historically demand for singles exceeds supply, particularly in the popular parts of campus.
It is important to have realistic expectations and an alternate plan if your first choices are not available. Every year is different, but historically singles on upper-campus will filled mostly by Rising Seniors. Rising Juniors looking for singles can expect lower-campus options to be available. Rising sophomores historically have found single rooms to be limited and possibly not available when they select.
Are any two rooms, at least one of which is a single, that both have individual doors leading to the hallway, but also have a door adjoining them. Because the adjoining door is lockable, the connecting singles can be selected individually or together.
The same rules apply as a double, triples, etc. . . both people would go through lottery together using the best time. Because these rooms are popular, and only for connecting singles, if you are pulling in an underclassman to a connecting single you will select at the end of your class year. For example: a senior wants to pull in a junior, that pair would choose their room after all of the other seniors have selected no matter what their lottery numbers might be.
Please Note: If a connected single is vacated after lottery that vacancy is managed by Residential Life. The ability to pick a "roommate" for these spaces is limited to the room selection process. Students living in connected singles may request a particular individual be placed in the adjoining room, but that request is not guaranteed.