A twin-boom aircraft is characterised by two booms (extended nacelle-like bodies) fixed to its main wing on either side of its . The booms may contain ancillary items such as fuel tanks and/or provide a supporting structure for external ancillary items. Typically, twin tailbooms provide mounting points for one or more tail surfaces, although on some types such as the Rutan Model 72 Grizzly the booms run forward of the main wing. The twin-boom configuration is distinct from twin-fuselage designs.