That's a great question, and a common headache for many of us! The absolute most secure way involves a multi-layered approach that goes beyond just a simple chain. Here’s what I’ve found works best, based on experience and community tips.
First, ditch the thin, lightweight chains and padlocks. They can be cut easily. Instead, opt for a heavy-duty vinyl-coated steel cable (like those used for bicycles) or a thick, hardened steel chain. Thread it through both handles or the designated anchor points on the trash can *and* through a fixed, immovable object like a sturdy fence post, deck railing anchor, or a ground anchor specifically installed for this purpose.
The critical second step is the lock. A quality, weather-resistant padlock (shackle diameter of at least 10mm) or a combination disc lock is essential. Make sure the lock's shackle is too small to be snipped by bolt cutters easily. For a cleaner look, you can use a lockable trash can strap made of steel cable with an integrated combination lock—these are designed for this exact purpose.
For ultimate security, especially against persistent animals like raccoons or bears, combine chaining with a bin with locking lids or use bungee cords with hooks to secure the lid itself. Placing your chained and locked can in a locked enclosure (a shed or a dedicated bin cage) is the gold standard.
Remember, the goal is to create multiple points of difficulty. A determined thief or animal will move on to an easier target. Secure the can to something solid, use a tough cable or chain, and finish it with a reliable lock. This method effectively deters theft, prevents scattering by wind, and stops most pests from making a mess.