Rust keycard puzzles are a ladder. A green card and a fuse open a green room, which holds a blue card. A blue card (sometimes with a green one and a second fuse) opens a blue room, which holds a red card. The red card opens the top rooms at Launch Site, Military Tunnels and the Missile Silo. Since the October 2025 Meta Shift update the rooms also hold the blueprint fragments you need for Workbench Level 2 and 3, so running them is no longer optional progression.

How a puzzle works

Most rooms follow the same pattern: find the fuse box, slot an Electric Fuse, flip it on (sometimes after hitting one or two switches elsewhere in the monument), then swipe the card at the powered reader. The fuse only powers the reader for a limited time, so do the switches first and the fuse last.

Cards wear out. A green card loses 25% condition per swipe, even on a door that is already open, and cannot be repaired. Do not swipe for fun.

Fuses drop from brown crates (14.3%), tech parts crates (26.5%, one or two), underwater crates and some scientists, and very rarely barrels (1.4%). A fuse recycles for 24 scrap at a monument, which is a bad trade if you have a card to use.

Reset rules (since November 2025):

  • A room's refresh timer only starts once a player loots a container inside it.
  • The timer keeps ticking even with players nearby.
  • Ten minutes before a refresh, radiation covers the switches and fuse boxes.
  • The puzzle only resets after the area has been clear of players for a total of five minutes.

Getting a green card

Green cards spawn for free at the Lighthouse, Oxum's Gas Station, the Abandoned Supermarket and the Junkyard. Standard scientists also drop one or two with a 36.3% chance. The Outpost no longer sells blue cards (removed in November 2025), so you have to climb the ladder yourself.

Green puzzles (reward: blue card)

All green rooms need a green card and one fuse, and each has one Basic Blueprint Fragment along with crates and the blue card.

Monument Needs Notes
Sewer Branch Green + fuse Low radiation, good first run. Room has 3+ basic crates
Small and Large Harbor Green + fuse Card trailer marked H2, fuse box in a nearby trailer
Satellite Dish Green + fuse
Dome Green + fuse Added October 2025, room has a recycler
Ferry Terminal Green + fuse Added October 2025
Radtown Green + fuse Added October 2025

Blue puzzles (reward: red card)

Each blue room has two Basic Blueprint Fragments sitting next to the red card.

Monument Needs Notes
Water Treatment Plant Blue + fuse Also a separate fragment spawn elsewhere on site
Train Yard Blue + fuse (green optional) Optional green room has 1 more fragment
Airfield Green + blue + 2 fuses Scientists guard the Armory
Power Plant Green + blue + fuse 3 Basic fragments across both rooms
Arctic Research Base Blue

Train Yard route. Hit the switch on the generator in the recycler building, then the switch on the balcony of the tall tower. Go to the back of the main building, fuse in the ground floor box, then up to the blue door.

Airfield route. First fuse goes in the office building box. Take the tunnel entrance between hangars 2 and 3, turn left, green card on door 3. Second fuse at the box near the Armory, blue card in. The red card is inside.

Power Plant route. Through the green doors, hit the switch on a generator, then follow the signs through Storage to the Control Room for the fuse and blue door. Since Power Trip, the generators in the green room also take the heavy fuses that power the grid.

Red puzzles (reward: Advanced Blueprint Fragments)

Advanced fragments always spawn in pairs and are what Workbench Level 3 needs.

Monument Needs Reward
Launch Site Green + red + 2 fuses 2 Advanced fragments
Military Tunnels Green + blue + red + fuse 2 Advanced fragments
Nuclear Missile Silo Red 2 Advanced fragments, elite crates
Small Oil Rig Blue + red Locked crate with Advanced fragments
Large Oil Rig Red (plus green and blue doors on the way) Locked crate with Advanced fragments

The Missile Silo became a red card monument in October 2025 and got three extra elite crates. The reader is in the small building left of the main entrance; after swiping, press the button and the hatch stays open for 20 seconds. Bring at least 25 radiation protection for the underground levels, and know that the only way out is finishing the run and leaving through the back exit.

Hackable locked crates (Oil Rigs, Cargo, Chinook) are guaranteed to hold Advanced fragments, and elite crates have a 1 in 10 chance.

Monument blockers. Since the September 2026 Breach and Clear update, monuments with red rooms have blockers in the way. They take heavy damage to break (some weaker ones can be meleed), do not respawn once destroyed, and start decaying if nobody breaks them within 24 hours. Bring explosives or wait for someone else to open the path. The raid calculator helps if you are budgeting boom.

Heavy fuse rooms

The October 2026 Livestock update added a second layer of locked loot rooms at Airfield, Ferry Terminal, both Harbors, Junkyard, Launch Site, Military Tunnels, the Missile Silo, Radtown, Sewer Branch, Train Yard and Water Treatment Plant. They open once enough heavy fuses are in the Power Plant, and the count varies by monument. Facepunch has not published the exact numbers, so check the door when you get there.

Run order

  1. Grab a green card and two or three fuses. Lighthouse, Gas Station, Supermarket or Junkyard for the card; brown crates and tech crates for fuses.
  2. Nearest green room. Sewer Branch, a Harbor or Satellite Dish are the easiest. You leave with a blue card and one Basic fragment.
  3. Blue room. Water Treatment and Train Yard need only one fuse. Airfield needs two plus your green card again. You leave with a red card and two more fragments, three total.
  4. Two more Basic fragments (military crates, airdrops, another green room) and you can craft Workbench Level 2. The workbench and tech tree guide has the full costs.
  5. Red room when you have a kit. Launch Site and Military Tunnels are the standard; the Silo only needs the red card but locks you in with heavy scientists.

Every crate in these rooms also feeds your scrap, so pair the run with a recycler on the way home. The scrap farming guide covers the rest of the loop.

Sources