Gather all your materials.
You will need a P1 Power, a Makey-Makey module, a servo, two alligator clips, stick dots, Legos, or any other construction material, lock box with a key, and two three-ring-binders with metal rings. Optional: magnets and mounting board.
Build a box-like structure
Use Legos to build a box-like structure to hold the key.
Attach the servo
Attach the servo on the corner of the roof using glue dots or any other sticky material. Optional: attach the magnets to hold the key.
Make false roof
Use a flat Lego piece to make a false roof so that the servo can easily lift the roof.
Build the circuit
Build the circuit attaching the P1-power - Makey-Makey - Servo. Optional: attach it to a mounting board. Put the circuit in one of the three-ring-binders.
Attach the alligator clips
Attach one of the alligator clips to the metal on the first three-ring-binder. Attach the other alligator clips to the metal on the second three-ring-binder.
Place the lego box and the three-ring-binders on a bookshelf. When you touch the metal on both of the three-ring-binders, you close the circuit causing the Servo to move opening the false roof and revealing the hidden key.