Rust Blue Keycard

Blue keycards are found inside the room a green card unlocks. Swipe a green card at a monument's green puzzle and there's typically a blue card waiting inside — so you spend a green to earn a blue.

11 monuments use the blue keycard: Small Oil Rig, Train Yard, Airfield, Ferry Terminal, Power Plant, Radtown, Water Treatment Plant, Large Oil Rig, Launch Site, Military Tunnels and Missile Silo. Swipe it at that monument's card reader to open the puzzle door.

Finishing the green-card puzzle at Harbor, Satellite Dish or Sewer Branch rewards a blue card — spend a green to earn a blue. Catfish, Orange Roughy, Salmon and Small Shark each have roughly a 1-in-5 chance to give one when gutted.

No — keycards can't be crafted, and the only card sold anywhere is the red one (at Bandit Camp). The way to get a blue keycard is to loot one: it's waiting inside the room the previous card unlocks, or gutted from higher-tier fish.

Yes — a keycard is consumed the moment you swipe it at the reader, so you need a fresh one for each run. Grab spares if you plan to chain several monuments in one trip.

The Red Keycard. Red keycards sit behind a blue-card door, almost always at the larger monuments. You spend a blue card to reach the room that holds a red one, then use the red for the final loot room. It's also the one card you can buy: Bandit Camp's Scrap 4 Sale vendor sells it for 40–160 scrap.