This simple measuring tool fits in your pocket or a tool drawer and circumvents using the measuring tape, which is less accurate and more work for quickly determining the depth of a piece of wood in the scrap bin.
Step 1: Open up Illustrator and make a Rounded Rectangle
Use the Rounded Rectangle tool, make a 3" x 2" rectangle. Set the stroke width to .001 for laser-cutting (or whatever your laser-cutter requires for vectors). A 3-inch by 2-inch piece piece of acrylic comfortably fits in your pocket.
Step 2: Create slots for the material
Create rectangles that are 1.25" wide and for the height, the thickness of each sheet that you want to measure.
Step 3: Position slots
Step 4: Pathfinder subtraction
Step 5: Add fractional numbers
Just in case you're not familiar with laser-cutting, you will have to use Create Outlines to convert text for raster-etching.
Step 6: Laser cut and use
I left the paper on for better text legibility.
I've included the Illustrator file (the text hasn't been converted to outlines just yet).