Welcome to the Spyderco Forum. As simple as possible, the right-handed compression lock knives (PM2 etc) have the access to the lock on the right side. So it's easier to operate with your right hand. The left-hand version is opposite. He should still be able to operate his LH knife with his right hand but it's not quite as easy as it would be with a RH knife. I operate my RH compression locks with my left hand often but I wouldn't want the LH version. I'd suggest that your wife return the knife she bought and get him the RH one.
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