start from scratch
With no help from anything done before; from the beginning; from nothing.
Dick built a radio from scratch.
In sewing class, Mary already knew how to sew a little, but Jane had to start from scratch.
put one's money on a scratched horse
To bet on a certain failure; to gamble without a chance of winning.
You bet on the New York Mets to win the World Series? Why put your money on a scratched horse?
scratch around for
To search randomly for something.
If you scratch around for a more reliable used car, maybe you'll feel more confident on the road.
scratch one's back
To do something kind and helpful for someone or to flatter him in the hope that he will do something for you. Usually used in the expression You scratch my back and I'll scratch yours.
Mary asked Jean to introduce her to her brother. Jean said, "You scratch my back and I'll scratch yours."
scratch the surface
To learn or understand very little about something. Usually used with a limiting adverb (as only, hardly).
We thought we understood Africa but when we made a trip there we found we had only scratched the surface.
High school students have only scratched the surface of their subjects, and even after college graduation, they still find there is much more to learn.
up to par
up to the mark
up to scratch
up to snuff
In good or normal health or physical condition.
I have a cold and don't feel up to par.
The boxer is training for the fight but he isn't up to scratch yet.
As good as usual; up to the usual level or quality.
The TV program was not up to par tonight.
John will have to work hard to bring his grades up to snuff.