A few small changes can close a lot of the gap between a door opening and someone noticing. None of these guarantee safety on their own — think of them as layers, not a single fix.
Start with water, if it applies to you. Advocacy groups consistently point to drowning as the leading cause of death when an autistic child wanders, so if there's a pool, pond, or open water anywhere nearby, secure that path first — a self-latching gate, a pool alarm, before anything else on this list.
Layer alert and barrier. A lock slows someone down; an alarm tells you the moment they've gotten past it. You want both, mounted out of the direct line of sight — high or low on the door, wherever makes sense for the person's height and habits.
Make identification impossible to miss. A medical ID bracelet, a name and contact number sewn into clothing, or a wearable device — anything that lets a stranger or first responder act immediately instead of guessing.
Loop in the people around you. Neighbors, local police, and anyone who regularly spends time in the home should know that wandering is a possibility. A short description and a recent photo, shared in advance, can cut search time dramatically if it ever comes to that.
Reduce nighttime risk specifically. Wandering often happens when the house is quiet and routines are disrupted — a door or bedroom alarm for overnight hours covers a window that's easy to underestimate.
None of this replaces supervision. It buys you the seconds and the warning that supervision alone can't always provide.