This is the Arduino case made for Tecla. It can be easily modified to be an Arduino only case without the Tecla shield socket holes.

The case consists of a lid and a bottom portion. The lid slides into the grooves on the bottom piece and snaps securely into place.

Edit: The images are a bit old so there are a few small errors corrected in the sketchup files. Also, it looks like the holes in the case do not match the model Arduino board. This is because I took the measurements myself and found that the Arduino model was a bit off. The case worked in real life when fabricated.

I have included the files for all the pieces made with Google Sketchup. The top and bottom sketchup files contain the separate pieces for fabrication. The "everything" file contains all the pieces together along with an Arduino board for demonstration.