I prefer belt buckle
A tack in the glove is fine with me...
Unless Joe Niekro was a master illusionist I can’t see him using a nail file in his back pocket. I can see him using something else on his junk pitches that made them move and cut, and that nail file happened to be in his pocket for his knuckleball pitch for his finger nails.
Freegards
I prefer belt buckleSo did Whitey Ford----after he finally got nailed (sort of) using his wedding ring, which had a tiny rasp in it but enough that, as he once put it, "I had my own tool bench out there."
When Ford couldn't go to his belt buckle, catcher Elston Howard had a trick: he'd scrape a ball against the buckles of his shin guards before returning it to Ford.
Of course, in the old days you could go to the toxic waste dump if you chewed tobacco. That was Lew Burdette's little trick: he'd spit the juice to a certain part of the dirt near the rubber and build himself a little sump puddle. Whenever he went to adjust his shoes (which was half the time, a habit he'd had since he was a Yankee farm hand), he'd scoop up a little of his contraband puddle if he needed an out pitch post haste.
Joan Crawford may or may not have screamed "No! Wire! Hangers!" at her daughter . . . but Mike Flanagan of the Orioles didn't mind them when it came to demonstrating what he could do with a doctored ball if he wanted. He once showed Thomas Boswell a fresh ball, broke open a wire coat hanger, scratched four parallel cuts into the meat of the hide, then held it up. "Any time I need five new pitches," he said, "I got 'em."