Great job, Tim.  I made several of those in different sizes and types of wood for my wife's piecing rulers.  She took them to quilt guild and I started making more for the ladies.  Then she got a long arm quilt machine and started buying rulers for that.  She showed them at a couple of quilt shops and so I started making them to sell.  I use 1.5" thick lumber and usually about the same dimensions as yours.  I use the thicker lumber for long rulers and the thicker long arm rulers.  That way I can cut the groove 0.75" deep to give it a good hold.  I've found this to be a great use for short cutoff pieces that might have wound up in the burn pile otherwise.  Thanks for sharing.
Steve