After looking at the fish measureing boards on Cabella's I got to thinking about what they really are. Just a metal rule bent up at one end. Reviews for these boards are mediocre and most complain that the measurements are hard to see and read. Also at $18 not including tax and shipping I thought they were a bit expensive.
My solution: I bought a 48" drywall T-square at Home Depot for $10.97 and some tax. These are made of aluminum and coated with a yellow powdercoat finish. The scale is printed in black and are very large and easy to read.
Using a hand grinder I ground the backs off the rivets and removed the T-bar. It will make a great straight edge in the shop for other things.
The end of the scale then has about 2" worth of material which can be bent up just like the ones you find online so that the nose of the fish can be placed up against it. I cut mine off at 25 1/2" using my bandsaw.
Finally I use a fine tip sharpie marker to write the limits and sizes on the back side of the rule. I also draw lines across the front side to quicly show the slot size restrictions for each type of fish, Largemouth, Smallmouth and Walleye. The marker can be rubbed off at the end of the season with brake clean on a rag. Bass Boat Saver can be used to clean the scale without removing the sharpie marker.