The easiest way to get both is to buy them from CelesteEmbark Studios
Looting drawers and cupboards in residential areas like Pendola Pass's Old Town is good for planksEmbark Studios
These yellow drawers in Stella Montis' Assembly area seem to be a guaranteed sheet metal dropEmbark StudiosKey deets
🛠️ You can buy planks and sheet metal from Celeste.
🛠️ Or find them in residential/old world and technological/industrial areas respectively, though they can appear anywhere it seems.
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