flaps= Freindly Local Auto Parts Store. It's one of the many acronyms used on the site.
The knurl I speak of is the outside diameter of the balljoint housing, where it has a "ribbed" section that grips the hole in the control arm. Factory balljoints are usually smooth in that area, as it is an interference fit. Aftermarket balljoints (or at least the good ones) have the ribbing, which makes it slightly oversize and helps it hold tight, especially if the hole isn't quite std size. It's the same concept as the ridged part on a wheel stud. The parts store should be able to mic it for you, a simple dial caliper would be just fine for measuring them.
