Left: hill 冈 (image of a hill), right: cutting/knife 刂
(Cartilage in the meat?) A "hill" (= a thickening) is for cutting with a knife: particularly hard.

Left: metal 钅/金, right: hill 冈 (=岡 Here as a bloomery hearth for steel smelting, in which iron ore and charcoal were stacked alternately as a hill).
The metal from this hill (= oven) is steel.

Left: thread 纟/糸, right: hill 冈/岡
Threads and equally also hills can be guiding principles.

Top: mountain 山, below: hill 冈/岡 (image of a hill)
The mountain and hill stand for the elevated position of a guard and generalized for a position or job.

Outside: frame 冂, inside: cross 㐅 (simplified from 岡)
Image of a hill, where the cross emphasizes its size.