This DIY project is totally doable. It took me a few days worth of nap times, but doesn't require any special tools or skill.
board (I used a 2" x 6" x 6' pine board (about $7 at Home Depot)
stain (I used Minwax Polyshades--love this stuff!--in Espresso Satin)
I started out with my 2"x 6" x 6' pine board.
This shade can get pretty dark, but with only one coat, it was perfect for me. I love how it really emphasized the grain and "movement" of the wood. Beautiful!
First I had to measure off the inches. This plunged me into an unexpected decision: how long did I want each line. Some boards that I saw on Pinterest had all the lines the same size; others looked more like a ruler with different sized lines. I ultimately decided on the varied line lengths corresponding to 1/8, 1/4, 1/2, etc... (except each mark measured an entire inch rather than a fraction of an inch). And after experimentation, I made the foot marks 2" long, 1 and 2" were 1/2" long, 3" was 1" long, 4 and 5" were back to 1/2" long, 6" was 1 1/2", 7 and 8" were back to 1/2", 9" was back to 1", 10 and 11" was back to 1/2", and then I came back to the 2" long foot line. (That sounds really complicated! Just look at my finished product and hopefully you'll understand what I mean...)
Then it was time for the numbers. First, you scribble the back side with pencil, so that the lead will transfer onto the wood. I'm not sure this is totally necessary since you're making an indentation anyway, but this part is pretty easy and I think the lead helped me to see the lines a little better.
Finally, I decided on black, and simply used a black Sharpie, which I have tons of. It came out really good and I really liked it...until I pulled my face away and realized that the letters/numbers were barely visible since the stain is so dark.