Shifting

Shift·ing

Changing in place, position, or direction; varying; variable; fickle; as, shifting winds; shifting opinions or principles.
Adapted or used for shifting anything.

Shifting backstays: temporary stays that have to be let go whenever the vessel tacks or jibes.
Shifting ballast: ballast which may be moved from one side of a vessel to another as safety requires.
Shifting center: See Metacenter.
Shifting locomotive: See Switching engine, under Switch.