A lighting device (30) comprises a side-light light guide 1′ located in a support (2) that has an elongate opening for the passage of light emitted by the light guide. The support (20) is shaped to provide contact edges (24) and the only physical engagement between the support and the light guide is along those contact edges. The support also has planar surfaces internal positioned adjacent, and parallel to, planar surfaces (15) in the light guide to retain the light guide in the required orientation in the support. To enhance the flexibility of the support, in some embodiments only part of the support is continuous along the whole length of the support (FIGS. 14 to 19).