From Longman Dictionary of Contemporary Englishback onto something phrasal verbOPPOSITE/FACEif a building backs onto something, its back faces it The hotel backs onto St Mark’s Square. → back→ See Verb table
Examples from the Corpus
back onto • The development is sited three miles from Weston town centre and backs onto green belt land.• Burun had rocked back onto his heels.• He turned back onto his left.• Howard sinks back onto the day-bed.• I steered the car up the on-ramp back onto the freeway.• Wildfowlers would like to get redshanks back onto the list of birds which can be legally shot.• Coming off yet another knee injury, Masakayan took longer than usual to get back onto the sand.• Three were dragged back onto the train and taken by the scruff of the neck from station to police car. 