工时

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.

时 = 寸 + 日 : Mnemonic symbol: a giant pocket watch.

The sun (日) asks Sherlock Holmes (sh) out for a coffee in the space station's kitchen (Ø2). Looking at his pocket watch (时), Sherlock sees he has time, winks and "thumbs up" (寸).