At top is a side view drawing of a full-scale, trailer-based system designed for double-sided gamma and neutron source search. This is the view that would be seen from the front (or back) of the trailer. A central detector array consists of organic scintillator on top (blue) and inorganic scintillator on bottom (orange). The lateral offset between the different scintillator types allows room for PMT readout for each detector. On either side of the trailer, there exists a dual layered mask made of lead (red) and organic scintillator (green). Additional lead (white) is added to reduce the gamma background. At bottom is the view that one would see standing in between the detector plane and a mask plane, facing the detector plane or toward the side of the trailer.