Permafrost: How to Unlock Locked Doors with the Stone Shiv (Fixing “Unsuitable Tool Used!”)

A locked door in Permafrost will not open with an axe, a pickaxe, or empty hands. Walk up to one and you get the label “Doors” with a small padlock and the prompt “Hold F Unlock,” plus a knife icon on the left. That icon is the game telling you which tool it wants, and the first knife you can make is the Stone Shiv.

Quick answer: Craft a Stone Shiv (1 Stone, 2 Wood), press its quick-slot number to hold it, then hold F for about three seconds until “Knife used to Unlock” appears and press F again to open.

At the first cabin of Permafrost the door reads “Doors, Hold F Unlock” with a red knife icon; holding F with the Stone Pickaxe in hand gives “LOCKED, Unsuitable tool used!”, then the Stone Shiv is equipped, the icon turns white, holding F gives “Knife used to Unlock” and “LEVEL UP! Lockpicking”, and F opens the door.

What the locked door shows you

This comes up during the first quest, A New Beginning, at the opening objective “Open The Cabin Door.” A yellow quest diamond marks the door on the first cabin’s porch. Climb the stairs until the interaction prompt appears.

Yellow quest marker over the cabin door during the A New Beginning objective — The A New Beginning objective is active, with the yellow marker highlighting the cabin door as you walk up to it.

The key detail is the knife icon to the left of the word “Doors.” It is red while the correct tool is not in your hand. It turns white the moment a knife is equipped. If it is red, the lock will refuse you no matter how long you hold the key.

The cabin door marked 4m ahead with the Hold F Unlock prompt — The objective marks the cabin door a few meters ahead as you close in on the porch.

Why “Unsuitable tool used!” appears

Hold F with the wrong item in hand and a banner reads “LOCKED” with “Unsuitable tool used!” The door stays shut. You will see this with a Stone Pickaxe, a Stone Axe, or nothing equipped at all. The lock only responds to a knife.

The Hold F Unlock prompt failing because a stone pickaxe is equipped — Holding F with the stone pickaxe in hand triggers the “Unsuitable tool used!” message and the door does not budge.

Two errors have the same outcome, even if you own a knife. The Stone Shiv must be equipped in your hand, not merely placed in the quick bar. Keep F held down for the unlock instead of tapping it once.

The interaction key is F. E is the companion command, so pressing it does nothing to the door.

Craft the Stone Shiv at the start

You can make a Stone Shiv straight from your inventory, with no workbench, for 1 Stone and 2 Wood. Both materials are right next to the first cabin.

Stone: the small stones on the ground, prompted as “Rock Shard, Press F to pick up,” give 1 Stone each. They sit around the boulders in and beside the frozen stream.
Harvest a “Bush, Press F to harvest” to get 1 Wood and 1 Edible Root. Bushes grow near the cabin stairs and on the other side of the clearing.

Press TAB to open your inventory, then check the CRAFTING list on the right. Its six starting entries, in order, are Crude Bow; Makeshift Bandage; Stone Axe; Stone Pickaxe; Stone Shiv; and Wooden Arrow (x3). Select Stone Shiv and press Craft x1. The finished tool goes into the first quick slot that is free.

The Stone Shiv’s tooltip lists 10 damage and a value of 10. For opening the cabin door, none of that matters beyond it being a knife.

Unlock and open the door

Stand at the door until the prompt reads “Doors, Hold F Unlock.” Check the icon on the left. If it is red, you still need a knife in hand.

Press the number key for the quick slot holding the Stone Shiv. Having it in the bar does nothing on its own; selecting it turns the prompt’s knife icon white.

Hold F for about three seconds. The circular timer fills and the banner changes to “LOCKED” with “Knife used to Unlock.” The padlock disappears and the prompt becomes “Doors, Press F Open.”

The Doors prompt at the cabin while holding F to unlock with a knife — With the knife equipped, holding F fills the unlock bar and the prompt switches from the padlock to “Press F Open.”

Press F once more. The door swings open and you can step into the cabin.

How to know it worked

Two things confirm the unlock. The “Open The Cabin Door” objective ticks off and the next objectives appear in the top left. A “LEVEL UP! Lockpicking” notice shows with a “K TO CHECK” prompt.

Unlocking the door does not consume the Stone Shiv; it remains in its slot. Unlocking doors and chests trains the Lockpicking skill, and the skill lowers the durability a lock costs the tool you pick it with.

What is inside the first cabin

The interior is dark, so press L to switch on the flashlight. It is also warmer than outside, which matters this early. While you stand in it without a fire, Body Warmth climbs back toward full.

The yellow-outlined basket displays “Quest reward, Press F to open” and contains 5 Cloth; a “Wooden Cabinet, Press F Open” provides 2 additional Cloth. Cloth is your next need: 2 Cloth can be used to make either a Rope or a Makeshift Bandage. Continue the quest by unlocking Rope in the blueprint tree, then craft a Crude Bow from 2 Wood and 1 Rope. By the time you reach the loot behind the door, the first knife has already come in handy.