Adsorption of Ga on the hydrogen terminated Si (100)–2× 1–H surface has been investigated by scanning tunneling microscopy (STM). We have found that the thermally deposited Ga atoms preferentially adsorb on the hydrogen-missing dangling bonds and on the surface impurities. We desorb hydrogen atoms by the STM current and fabricate atomic-scale dangling-bond wires, in the similar way as was reported by Lyding et al.[Appl. Phys. Lett. 64 (1994) 2010]. In order to fabricate more detailed dangling bond structures, several methods of manipulating (detaching, attaching and moving) the individual hydrogen atoms are tested. We are able to thermally deposit Ga atoms on a dangling-bond wire and fabricate an atomic-scale Ga wire on the Si surface.