The Lockwood Onyx is a pretty hardy and versatile residential sliding door lock commonly used on patio doors across Australia. Supplied with a 5-pin cylinder on both internal and external handles giving it the ability to be deadlocked, and double hooks to prevent the door being lifted and levered off the tracks, it is truly at the top of the list of glass sliding door locks available on the market.
However... it does have one common problem that can arise months or years after installation. The strike plate loosens and needs adjustment so that the hooks can locate.
Here's how to fix this common problem without calling a locksmith. It might not fix it every time, but it could save you some money.
In the photos below you'll see a 'pin' on the lock that needs to be pressed in by the strike to allow the two hooks to project out. There's no adjustment for the hooks themselves so don't take the lock apart; the work needs to be done on the strike.