Can someone tell me how to cut a 15 x 20 linear rail? I'm thinking maybe one of these might do it. (See attachment) Thanks

mostly it case harden so before you try a saw blade see if a file will cut part in not you could also use a circler saw with an abrasive blade

I would not even bother, that is super hard steel. Best way to do it is a grinding wheel, and dip it in water once in a while to cool it. This worked very well for me.

an abravise blade will cut rockwell 65 and so will a circler saw with an abrasive blade. that what abrasive blades are made for

The saw pictured will cut it just fine. I use mine to cut 60rc Thomson shafting, tool steel, and stainless... basically anything that I don't want to cut with my bandsaw for fear of destroying a perfectly good blade.

I would recommend using the saw away from your machine tools, preferably outside. It throws sparks like there's no tomorrow, and the abrasive dust can really do damage to precision parts.