Hers Truly loves playing with locks. She will try for long periods to open one with a key. The other night, I held her up for ten minutes while she tried. Last night, I used a stool.
I also let Hers Truly play in the car. Cars a great fun! They have steering wheels, stick shift, seats, pass through, and all kind of places to climb on. Best of all, that triangular thin on the dashboard makes a click-click sound while yellow lights go on and off. Great fun!