The Birtcher 71 series was originally built per a US Army standards and was specifically designed for use with Card- or Wedge-Loks, in cold wall applications, for PCB extraction only. As can be seen in the image on this slide, they have only one “leg”. They were designed this way to provide adequate clearance for the Allen wrench which accesses the hex drive in the Card-Lok screw head. Accordingly, these extractors come in left and right orientations, which denotes the open side (side without the leg). On each board, there would be one left orientation at the bottom and right orientation at the top of the PCB, or vice versa. Because of their design, they are compatible with all Card- and Wedge-Loks, even the larger profile 250 series.