In 5 minutes you could build yourself a Lego secret compartment that you can keep in plain sight.
Step 1: Materials
2 1x2 smooth pieces
12 1x4 pieces
12 1x6 pieces
2 4x4 flat pieces
1 6x6 flat piece
2 2x4 pieces
1 2x2 piece
4 1x2x5 (these pieces are 5 tall. if you cant find these pieces you could just use 1x2s.)
Try to use ans many of the same color as possible so it will look more realistic.
WARNING: be sure to read the annotations
Step 2: Base
First take the 1 x 2 smooth pieces and place them one in from the corner like shone below.
Step 3: Walls
Make sure the walls are 6 blocks high.(not including the baceplate.)
Step 5: Use
To use it put money,a key or a ring in it. now just slip the two parts together and your done! The best part about this is that you can put it in plain sight!