This is a stencil for Microsoft’s Visio 2013 for rack-mount objects.
The concept of this stencil is to make it very fast and easy to do the first planning stages for a rack project. The shapes / objects in this stencil are very abstract with just enough detail to easily identify what they are. They are all of the same scale, so you don’t waste time looking for stencils on the internet that fit together nicely.
In addition to that, everything is based on a 1U standard. That means if you have a physical piece of hardware that takes up 2U, you would stack two objects from this stencil to represent that 2U of space.
Here’s a video of it in action