A linear guide unit, in particular a gantry axis, that has an oblong guide support (14), is provided with two essentially parallel guide rails (24, 26) extending in the guide direction (F), but rotated in relation to each other around a rotation axis (V) parallel to the guide direction (F), each of which guide rails (24, 26) has at least one sliding carriage (36, 38) guided on it so that it can slide in the guide direction (F), the sliding carriages (36, 38) being connected to a sliding carriage assembly (36, 38) capable of moving as a unit in the guide direction (F). According to the present invention, the two guide rails (24, 26) rest essentially without moving play against at least two counterpart support surfaces (GF24, GF24L, GF24R, GF26, GF26L, GF26R) of the guide support (14) extending essentially in the guide direction (F), two of the counterpart support surfaces (GF24, GF24L, GF24R, GF26, GF26L, GF26R) enclosing a predetermined angle, preferably of at most 90.degree., between them.