In Battlefield Vietnam, C4 is issued to the USMC and ARVNEngineer kit. It can be thrown and stuck on any surface, including vehicles and emplacements. After placing the block, the user switches to the detonator to detonate the explosive.
C4 is used to demolish vehicles, defend flags and can also be used as a last resort in close quarters. As it sticks on surfaces, it can be used to booby-trap enemy vehicles. A useful tactic is to sneak into an enemy base, find a vehicle, place it and detonate it as soon as an enemy enters it. An engineer is given a total of 5 blocks of C4.
Because Battlefield Vietnam features different loadouts for each faction, this list may not be specific enough. Please see each faction's respective page for information on individual weapon kits and loadouts.