Just need the quick answer?
Lower the cot mattress to its lowest setting, remove anything your toddler could use as a step, and keep bedtime calm and predictable. Red Nose Australia says that once your toddler is trying to climb out of their cot and looks like they might succeed, it's time to move them to a new sleep space, usually between 2 and 3½ years, but sometimes as early as 18 months.