Geometrical setup for the bldisk model. Blackbody seed photons from the neutron star are Comptonized in a boundary layer extending up to some latitude (orange region) and characterized by a given electron temperature kT_e and optical depth τ_bl. The other source of thermal photons is the accretion disk, where seed photons are emitted at the top of an electron-scattering atmosphere of optical depth τ_disk (green region). Some photons from the disk are Comptonized by the boundary layer, and in turn, the radiation emitted from the latter reaches the disk atmosphere and gets reflected.