Since the son of our friends got his first key and the installed a safety door recently, he had no chance to turn the key on his own.
I found several designs to overcome this problem but most were too bulky, involved attaching the plastic to the keychain (risk of loss!) and/or just weren't asthetic (personal taste)
Though I came up with a solution that is easy to print, requires no postprocessing (apart from glueing the two halves together) and looks cool enough for a growing up child.
Print the part twice, insert the key, **TEST IF IT STILL FITS TO YOUR DOOR** and apply some superglue to the plastic contact surfaces (no need to glue in the key).
My print did not wiggle at all and is a very tight fit with the KESO™ key. You might need to adjust your print settings if you print is too tight or loose.
c4t0r
