Child safety lock for door handle

"When little adventurers suddenly discover big doors…"
Our daughter figured out how to open the front door, and in no time, she was outside. To keep that from happening again, I quickly designed a simple but effective child lock.

The idea is straightforward:
The lever blocks the door handle. You can only press the handle if you push the lever aside at the same time. Once the handle springs back up, the lever automatically snaps back into its locking position, keeping the door safely shut until an adult deliberately opens it.

The lever axis is simply fixed to the door with double-sided tape, so no drilling or screws are needed.

This design is made for round door handles. Since the distance between handle and door surface can vary, you can simply scale the model (about +/-10%) without affecting its functionality.

For printing, I recommend PETG (because of the needed flexibility). PLA might also work, but I haven’t tested it yet.

Update – Version 2:
In addition to the original version, there is now a Version 2 of the child lock. This variant features an extended rear section that prevents the lock from being pulled forward off the handle. This small addition makes the mechanism even more secure and further reduces the chance that curious little hands can bypass it.

Update – Version 3:

After some time, my daughter managed to defeat the V2 version by pulling the lever underneath the door handle. To solve this, I created a V3 variant that completely prevents this bypass method.

V3 works best with round door handles, as the design relies on the consistent shape and movement of circular handles for proper function.