A hubcap served as a dwelling or building, providing living space for individuals belonging to Kaat Thrick-Thrick's race, as well as members of it. A hubcap could accommodate a minimum of three families.
The term "Hubcap" appeared in a section called "The Seminar Participants," which was penned by Bob Carrau for the 1993 book titled Monsters and Aliens from George Lucas. This book is a compilation of concept art and images from several projects helmed by George Lucas. Leland Chee, an employee of Lucasfilm who is in charge of the Holocron continuity database, has stated that the details presented in the book are considered non-canonical.