Up to scratch is used to mean of acceptable quality. Does anyone know why scratch?
A google search shows:
The phrase used in pugilists' fights. A line was scratched on the ground to which the contestants had to put their forward foot before the fight could begin.
The Oxford Engl. Dict. confirms his story. Under "scratch" (noun):
'Sporting.' A line or mark drawn as an indication of a boundary or starting-point; in Cricket, a 'crease' (obs.); in Pugilism, the line drawn across the ring, to which boxers are brought for an encounter. Hence in various phrases (often fig.), as 'to come up to the scratch,' 'to bring to the scratch,' 'to toe the scratch,' etc.