Basic Grilles

The grille is a simple device, so I use simple tools :-P

Here is the source document. We will select words from the existing text to construct our message.
Here is the basic outline for our key grille. I could cut this out or transcribe it to a more durable material but this provides a fully functional example with no muss and no fuss. Notice the alignment marks on the left edge. Those align with the top left and bottom right corners of the illuminated area. They are being used to ensure that the grille properly aligns with the source document.
The message is underlined below.
Below is an example from Cryptography the science of secret writing (Smith, 1955).