A single point operation for adjusting the height-of-cut of a lawn-care apparatus (100) provides cranked axles (300) linked together via a sprung link arm (150) coupled with a detent arrangement (145) moving and locking all four lawnmower wheels into the pre-determined positions, and therefore pre-determined height-of-cut.The present invention provides an improved spring unit (200) for biasing against the weight of the lawn-care apparatus (100) when adjusting the height-of-cut position of the lawn-care apparatus (100).