That checkering tool is called a "jointer". Brownell's has their own line, but personally I like the one made by Gunline.
I used mine for years - it insures that your starting lines are nice and straight, as well as the border, if needed. On longrifles, it makes a nice straight grove along the fore end or along the bottom of the stock parallel to that bottom line. Eezy-peezy.
Unfortunately for you, Brownell's is currently out of stock on both their own AND Gunline's. Their are other suppliers out there. Somewhere. Once in a great while, MidwayUSA has some checkering tools available,
I currently have an order in at Gunline for some scrapers. They took the order and the money, when I checked Monday, they said they would "check on the order". There are only two people there, you'd think he know if he made some scrapers or not. Only credit cards, BTW - no PayPal.