An implant is described for use in the spine, including two blades attached to a blade actuating member. Each blade includes a protruding portion that engages a corresponding channel in the blade actuating member. The blade or blades are extended or retracted when the blade actuating member is translated along a first axis. Each blade is retained in channels within the blade actuating member, and channels within the body of the implant, that constrain each blade to move in a direction near perpendicular to the direction of motion of the blade actuating member.