Walking into Bunnings to buy a deadbolt is overwhelming. There's a $35 option and a $400 option and they both look about the same on the shelf. Here's what the security ratings actually mean and what matters in real-world Bendigo conditions.
The Australian standard
Australian residential locks are rated by AS 4145, which categorises them by security and durability. The rating you'll see on packaging is "SLn" where n is 1-8. SL1 is basic, SL8 is high-security commercial.
For a normal Bendigo home, SL4 or SL5 is the sweet spot. SL1-SL3 are too basic for an entry door. SL6+ is overkill for most homes (commercial-grade construction, higher cost, but the difference in real security from SL5 is small).
What the grades actually measure
Durability: how many cycles before the mechanism wears out. SL4 is rated for 100,000 cycles, SL6 is 200,000+. For comparison, a busy front door does about 5,000 cycles a year, so an SL4 lasts 20 years in normal use.
Strength: how much force the latch resists before the bolt gives way. SL4+ resists basic kick-in attempts.
Pick resistance: how easy it is to pick the lock cylinder. Higher grades have anti-pick pins and tighter tolerances.
Brand recommendations
Lockwood (Australian-owned, widely available, good warranty support): solid choice for most Bendigo homes. Their Paradigm and Cylindrical Knob lines are SL4 and reliable.
Whitco (older Aussie brand, still made in Australia): traditional sash window locks and entry locks. SL4-SL5.
Gainsborough: budget end of decent brands. SL3-SL4. Fine for internal doors but step up for external.
Yale: good for retrofits and smart lock integration. Generally SL4.
What to avoid
No-name brand locks under $50. Anything not rated against AS 4145 (no rating on the packaging means it hasn't been tested). Locks with a single-cylinder when you're putting them on a door with glass nearby (a single-cylinder can be turned from inside if the glass is broken).
Installation matters more than the lock
The most secure deadbolt in the world is useless if it's screwed into a thin pine doorframe with 15mm screws. Make sure the strike plate uses 75mm screws into the wall stud, not the frame moulding. A well-installed SL4 lock beats a badly-installed SL6 every time.