Cheap brodifacoum rat blocks (same active ingredient as most of the stuff in Bunnings).
Handle with care and keep away from non-target species.
Always use a bait station. Too many pets and possums die from this stuff.
Recommended bait station:
https://www.amazon.com.au/Bainbridge-A3163-Bait-Station-Larg…
This is quite a lot of rat poison FYI. Unfortunately, I have an abandoned house/yard next door which rats have turned into a stronghold.
Very worry that the rats could die in inaccessible corners or even worse in the walls