|on the fringe
||not familiar, radical, not mainstream
||The Canasaurus Party is new - definitely on the fringe.
|on the fritz
||not operating, broken, out of order
||The VCR is on the fritz again. We can't watch videos tonight.
|Several conjectures about the origin can be found on www.worldwidewords.org/qa/qa-ont4.htm
|on the go
||busy, not stopping to rest
||We've been on the go all day, shopping and preparing food.
|on the ground floor
||(See get in on the ground floor)
|on the heels
||immediately after, following
||On the heels of the typhoon was a five-day rain.
|on the lam
||running away from the police, lay low
||When he's not in jail, he's on the lam - always running.
|on the limp
||limping, walking with a leg injury
||Norman is on the limp today. He sprained his ankle playing ball.
|on the loose
||free, running around, not in a pen or cage
||The zoo notified the media that a giraffe is on the loose.
|on the make
||looking for romance or sex
||Most of the men in the bar were on the make, looking for action.
|on the mark
||accurate, correct, dead on, spot on
||Your answer is right on the mark. Canada became a country in 1867.