whetstone, polish
砺 centers on the action of sharpening or smoothing with a stone: a whetstone used to polish blades or refine surfaces.
砺 combines 石 (stone) with 厉, which likely contributes the sound and the idea of grinding or sharpening. The exact historical development of 厉 is uncertain.
The left side is a stone 石, and the right side 厉 looks like a blade being drawn across a surface. Picture a whetstone polishing a blade to a sharp edge.
For レイ, imagine laying a blade flat on a whetstone: lay -> レイ, and the stone polishes the edge.