to prick, to cut blocks, to engrave
剟 centers on precise, forceful removal or marking: pricking, cutting blocks, or engraving. Each meaning involves a sharp tool separating or shaping material.
剟 combines 叕 (likely phonetic) with 刂 (knife), suggesting cutting or engraving with a blade. The exact historical development of 叕 is uncertain.
The left side 叕 looks like a series of connected marks or cuts, and the right side 刂 is a knife. Imagine a knife repeatedly pricking and cutting to engrave a pattern.
For テツ, picture a sharp metal tool (鉄, てつ) being used to engrave: 鉄 -> テツ, and the knife 刂 cuts into the material.