We're building a simple box which can be opened with a servo. I used a cheap plastic box with an unhinged lid. I needed a hinge of some sort. Two layers of packing tape worked great here.
Latching the box closed was as simple matter of taping the servo to the side of the box. I used double sided foam tape for this. A small piece of plastic helped to space the servo off the treat box lip.
I'm using the Arduino Servo library, with the servo connected to PWM output on the 'duino.
I should note her that I'm doing a terrible thing - I'm running the servo from the Arduino's own power regulator. Servos pull a lot of current, and can quite easily cause the Arduino to reset - or even harm your computer when running on USB. Things worked for me in this hack though.
If you're curious why I did this, it turns out that all my AA battery cases were packed and moved to my new shop as outlined in #New House, New Shop (Hey, did you know that hashtags allow you to quickly link projects anywhere on hackaday.io?)