工礦

工 = 二 + 丨 : Mnemonic symbol: a steel beam, since 工 looks like the cross section of a steel beam. In front of the engine ((e)ng1), Gitta Giraffe (gu) is doing some hard work: She's stacking a capacitor (二) on a dinosaur bone (丨) on a capacitor (二). She's not very successful, but then she gets the idea to use steel beams (工) as support.

矿 = 广 + 石 : Karl Koala (ku) got a new job at the coal mine (矿) in the anglepod's bathroom (ang4). The entrance to the tunnel lies quite high, so every time Karl brings out another coal stone (石) he attaches it to a small parachute (广) and lets it fly down to the floor.