LOOK AT DORMANS CATOLOG BUT THIS IS HOW I DO IT AS THE KNURL SIZE OF NEARLY ALL I SEEN ARE NOT WHAT THEY SAY,YOU CAN DRILL YOURSELF ALSO YOUR CENTER HOLES ARE THERE. USE A BIT YOU MIGHT HAVE OR BARROW,MINE REQIURED A 9/16'' BIT AS WAS RECOMENDED BUT THE STUDS WERE LOOSE AND ENDED UP GETTING BIGGER THAT FIT THE 9/16 HOLE BUT WAS THEIR RECOMEND TO USE A 19/32 HOLE .
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