This is a modified version of the Penrose "Impossible" Triangle which is an interesting example of how the brain can be fooled. The main difference in this version is the use of hardware to simulate the triangle side connections.
Note that this is a very simple project. It took about 10 minutes and was "free" since I used pallet wood and recycled bolts. I've included a drawing which is included in the video description.
Go to Instructables to see the build instructions:
Watching the video is the easiest way to see how it works