Heraldic courtesy

Heraldic courtesy or courtoisie is a practice typical of the heraldry of Germany, in which coats of arms are mirrored if necessary so that helms and animate charges, such as lions, face the center of a composition. This may be done in arms of alliance, as in the first illustration here; or within a single shield, such as that of the dukes of Guelders and Jülich in which the gold lion of Guelders turns to face the black lion of Jülich.
It can also be done on the left-hand side of a page of illustrations