Translational symmetry operations include:

Screw axis - Labeled “N_m”, indicating a rotation of 360°/N and a translation of m/N of a unit cell length. Shown below is a 2-fold screw axis (2₁) in which each element is rotated 180° about an axis and translated ½ of a unit cell length in a direction parallel to the rotation axis (the view in the left figure is perpendicular to the rotation axis; the right view is parallel to the axis):

There can be 2₁, 3₁, 3₂, 4₁, 4₂, 4₃, 6₁, 6₂, 6₃, 6₄ and 6₅ screw axes! Screw axes do not reverse the handedness of the molecule.