Getting the Yellow Key / Getting to the Yellow Key Slots

In the Meat Room, immediately deal with two Mounted Guns on the left and right, three Troopers, and a Pig Tank. The Yellow Key Door is at the far end.

Engage two Pig Tanks on the ground level and three Troopers sniping from higher shelves. Lure the Pig Tanks out before eliminating the Troopers.

Use the vents running through the shelves to take out a Mounted Gun and find an Atomic Health.

If you have a Jetpack, use a nook in the vents to reach the top of the shelves. Here you can find Shotgun Shells, two Large Medikits, Freezer Ammo, and Devastator Ammo.

From the top of the shelves, jump onto a crate to find an RPG and a Large Medikit.

SECRET 3: Destroy a crack on some boxes to access the beginning of the level and retrieve a Chaingun Cannon.

Return to the grates between the two shelves and follow them back past the Mounted Gun. You will find another grate leading into a room with two Enforcers and a Mounted Gun. Use a Pipebomb to clear this room before entering.

Inside this room, find three switches on the wall around a compartment. The combination to open it is X X O. The Yellow Key is inside.

A button on the wall opens a steel window for exiting this area.

Use the Yellow Key on the Yellow Key Door. Warning: A Commander and a Mounted Gun are waiting. Use the RPG as the Shrink Ray is ineffective against this Commander.

Shoot a switch on the roof to open the door further into the room.

Eliminate the Trooper behind shopping carts and the Enforcer within this room. The door here leads outside.