The Shark Lock Complaint That Became a Design Debate

A thread on r/knives started as a complaint and turned into one of the better lock-design arguments the subreddit has had in a while. The poster noticed that with his thumb resting on the jimping, scooting it backward would partially unlock his shark lock. After a couple of weeks of trying to get used to it, he was ready to go back to a Delica.

The replies split cleanly in two. One camp argued he was simply deactivating the lock with his thumb — pressing down and rearward on a lock designed to be pulled back — and that the fix is to stop doing the unnatural thing. The other camp argued that a lock you can accidentally disengage by holding the knife normally is a design problem, not a user problem, however clever the mechanism is.

The most useful reply came from someone who had done the diagnostic work. He described a slight catch that will not allow the blade to open further unless you really pull the lock back, which is difficult when pressure is applied to the blade or your thumb is on it. He compared it to a safety: you have to release it deliberately before the knife will move. Another user confirmed the same behavior on an AD20.5, needing an upward pull at the end of the rearward slide to disengage, and called it fantastic and fun anyway.

Then the thread got more interesting. One commenter reported having seen every variation of lock rock, lock slip, vertical play, and horizontal play on shark locks — not just on his own knives but on display samples at shows — and argued the lock geometry explains why. Another said he had emailed a dealer about the pull-then-back motion, was told the knife must be defective, sent it back, and got a replacement that behaved the same way.

That last detail is the takeaway. When a dealer's support desk cannot tell a design characteristic from a defect, buyers are left to crowdsource the answer. The lock either suits your hand or it does not, and the only way to know is to hold one.

Verdict: the shark lock rewards deliberate handling and punishes a death grip. If your thumb naturally sits where the lock moves, buy a back lock and be done — the Delica keeps earning its reputation.