Example of the emission-line and background apertures used when estimating the emission-line fluxes (and 1σ flux sensitivities) of the GLASS spectra of RXJ1347_00627 shown in Figure 2. The line flux is obtained by accumulating (“integrating”) the flux in the green ellipsoidal line aperture (﹩{E}_{{\rm{line}}}﹩). The red background aperture (excluding the red ellipse around the line aperture) is used to normalize the background level of the contamination-subtracted spectrum to account for over/undersubtraction of the local background (and contamination).