DCHP-1 Online
fix (someone's) flint Slang 
get even with; dispose of; take care of; spoil (someone's) chances.
- 1836 Oh no, if I didn't fix his flint for him in fair play, it's a pity.
- 1856 "Yes, I'll fix both their flints to-morrow. . . ." By "fixing their flints" Mr. Kennedy meant to express the fact that he intended to place his children in an entirely new sphere of action, and with a view to this he ordered out his horse and cariole on the following morning.
- 1942 "This day's the thirteenth o' November. Thank God it ain't a Friday or we'd ha' fixed our flint for keeps. . . ."
- 1836 Oh no, if I didn't fix his flint for him in fair play, it's a pity.