A device for insuring the congruency of opposed irregularly blocked fields

A device for insuring the congruency of opposed irregularly blocked fields has been developed which permits the treatment of both fields of a parallel opposed pair without the realignment of any field-shaping standard non-divergent blocks. The device is an adaptor which attaches directly to the shadow tray or wedge holder and provides 2 channels for 1 Lucite shadow tray. A mirrow-image field is obtained without disturbing the position of the blocking array. Set-up times are decreased.