Partition Specialties, PSI. Since 1958, PSI is the leading commercial interior specialty contractor in California and Norther ... n Nevada. Offering tailored architectural wall products and more. Our team and services are considered a valued resource and respected business partner by others in our industry. Exclusive West Distributor of: SkyFold Vertical Operable Walls, Modernfold Walls and Klein Door Systems. Offering: Tate Floors and other products; allowing for flexible space planning. read more