On the ZT0392 the front side is straight down. Index finger is forward of the tab or at least that is how I position to open it. It really doesn't need much of a jimping to open. As to why they add the jimping behind-- maybe aesthetics?
on the 220 jimping is good as my index finger if rearward tabbing it to open so those jimping helps with some grip on the finger as it pulls back.
on the 220 jimping is good as my index finger if rearward tabbing it to open so those jimping helps with some grip on the finger as it pulls back.