Scattered throughout multiplayer and campaign levels on Halo 2 and Halo 3 are UNSC crates, or large boxes, that contain supplies for ground based Marine forces. The contents of crates can be identified by their labels, and range from portable generators to armored boots. Although their only actual use in the game is cover from enemy fire, they do reveal a bit about the UNSC military, and play a key role in the enviroment of maps and campaign levels. They can also serve as cover or platform.
Halo 2
Crates
There is a range of different types of crates. This section contains information on all of them, ranging from smallest to largest. Kits are small crates that appear to be carried by Marine ground forces. Barrels contain liquid supplies. Small crates carry equipment used by ground troops, and large crates contain large pieces of equipment for use at fixed positions.
Kits
Rescue
The first crate can be found only once or twice in the game; it appears to be a small medical kit Marine medics would use to treat the wounded. It has the word "Rescue" along with the international medical symbol. It is likely able to be found in various campaign levels at Marine positions, but it can only be found once in multiplayer on the map Foundation.
Nerve Gas
This container can be found in a Brute encampment inside the armory, it is placed under another crate so it is pretty difficult to find. The crate has been spotted on the multiplayer map Foundation too. Perhaps it is with a bit of dry humor that Bungie placed this small crate right next to a medical kit within the same room.
Type: VX 7
Barrels
Blitz Can
This crate or barrel is for emergencies. You can also find blitz cans with Hydrogen fuel.
Item:Water-pure
Water
This crate (or barrel) can be found all over on multiplayer maps and Marine encampments in campaign. It appears to be a barrel of water for hygiene, cleansing, drinking, etc.
Type: Pure
Hydrogen
It's likely this is used by Marine ground forces to fuel various equipment, including generators and Warthogs.
Type: Fuel
Small Crates
Gas Mask
Gas masks are used by ground forces for protection against chemical or biological weapons.
Serial Number: 7880-53-413-1990
Type: S90
Item: Gas Mask/KR3/INF/BLK
Quantity: 64
Weight: 112 LBS
Lot: LYSE7Q409-53
Helmet
You'll find this on almost every Marine you encounter in Halo.
Serial Number: 9325-80-548-4127
Type: CH252
Item: Helmet/C-M/INF/W-OD
Quantity: 26
Weight: 82.6 LBS
Lot: TASA2G708-80
Body Armor
This for use by Marine ground forces for protection from energy and ballistic projectiles.
Serial Number: 2580-55-270-4193
Type: M52B
Item: Body Armor/C-M/INF/W-OD
Quantity: 12
Weight: 173 LBS
Lot: PILT4G312-55
Armored Boot
For use by dirt pounders.
Serial Number: 5893-22-418-2524
Type: VZ67
Item: Armored Boot/INF/V-OD
Quantity: 10 Pairs
Weight: 81 LBS
Lot: ROSW4C219-22
M6D Pistol
Perhaps the strangest box on Halo 2, it contains the Halo: Combat Evolved pistol.
REQ: Unknown
Type: M6D
Item: Pistol/M6D 12.7MM Rec. Op.
Quantity: 50
Weight: 204.5
Lot: PLTDN45145-81
Large Crates
Machine Gun
Used for base defense, this machine gun turret crate is found only on Headlong, Many Halo 3 maps(Forging), and various Campaign levels.
REQ: Unknown
Type/Item: M247 7.62 Gas Op. Auto Linkless
Quantity: 1
Weight: 893 LBS
Lot: VOYN3PV25-71
Emergency Food Prep Station
When a Marine is hungry, it's always an emergency.
REQ: Unkown
Type: MK71
Item: Emrgncy Food Prep. Station
Quantity: 2
Volts: 220
Weight: 716
Lot: ROSW4C240-92
Replacement Transfer Case
A transfer case is a part of the four wheel drive system found in the Warthog. The transfer case is connected to the transmission and also to the front and rear axles by means of driveshafts. The transfer case receives power from the transmission and sends it to both the front and rear axles.
REQ: Unknown
Type: D90Z
Item: Rplcmnt Transfer Case/M12LRV IDPG FT-DR
Quantity: 16
Weight: 203 LBS
Lot: LYSE7Q409-31
Security System
Security is a necessity for Marine encampments to protect against attacks.
REQ: Unknown
Type: SL23
Item: Auto/Sec/Mon/System
Quantity: 32
Optical: 8
Digital: 4
Weight: 305 LBS
Lot: TASA26700-92
Portable Generator
This portable electric generator/hydrogen fuel cell is likely used at fixed positions for power.
REQ: Unknown
Type: PG000E
Item: Port EL Gen/HY F Cell 18 KV
Quantity: 16
Gallons: 9
Hours: 24
Weight: 273 LBS
Lot: PILT4G312-70
Supply Drop Pod
Drop Pods are dropped by Pelicans to quickly deliver ammunition to soldiers.
Type:C Capsule
Lot:0722657