This is my version of a frame brace for a Creality CR10S as I think many of the others on Thingiverse are too large and complicated.
Left and right braces are the same so print two of each. It uses M8 threaded rod but 5/16" would do as well. I'm using M4 button head screws and T-nuts to attach to the frame. There's a small recess in the brackets so they fit over the original cap screws holding your CR10 together.
I stood them at 30 degrees so the supports were on the inside where they're hidden.
Designed in Fusion 360 - what a great program!