Level 3 Security

Samus facing a level 3 security door.

Yellow Hatches (Security Level 3) can be found throughout the Biologic Space Laboratories research station in Metroid Fusion. They are the yellow colored doors. To open them, Samus must find the Level 3 Security Station, located near the bottom of Sector 5. Once Samus has unlocked the doors, she can freely pass through them like normal doors by shooting them.

Interestingly enough, Yellow Hatches do not exist outside of Sector 5.