No constraints on lengths and angles

Two cell angles are right angles; no other constraints

All three angles are right angles; no other constraints

Fourfold axis of symmetry; All three angles are right angles; two equal cell lengths; no other constraints

Threefold axis of symmetry; Two angles are right angles; one is 120 degrees; two equal lengths; no other constraints

Sixfold axis of symmetry; Two angles are right angles; one is 120 degrees; two equal lengths; no other constraints

All three angles are right angles; all cell lengths are equal