A guidance mechanism (10) for a lancing device. The guidance mechanism (10) includes a piston (20) having a shaft (22), a plurality of wings or fins (24) extending from the shaft (22), a plurality of sliding engagement structures (26), and a lancet holder (28)； and a chassis (40) having a body (42), a plurality of longitudinal slits (44) or cutouts, a plurality of elongated engagement structures (46), and an end aperture (48). The piston slides within the chassis, and the wings/fins engage within the slits/cutouts, allowing for linear longitudinal guidance of the piston within the chassis.
