Lewis & Short

clābŭlāre, is, n. [clabula = clavula] a large, open wagon, probably with sides of wicker-work, used in transporting soldiers, Cod. Th. 6, 29, 2, § 2.
Hence, clābŭlāris (clāv-), e, and clābŭlārius, a, um, adj., of or belonging to the transport wagons: clavularis cursus facultate permissā, Amm. 20, 4, 11; Cod. Th. 8, 5, 62.