Heavy Traps are designed for exterminating D.A.V.E.s, Champions, and any other strong monsters that have the misfortune of encountering them. They can't be countered using weak monsters, owing to their specialised trigger system that only fires when strong monsters step on them. However, they cause splash damage to all nearby monsters.
Heavy Traps are best used with THDT (Town Hall Death Trap) / SDT (Silo Death Trap) for 100% efficient performance (for more information click here). Placing 3 Heavy Traps together will make enough firepower to destroy even the most powerful D.A.V.E. units and the Zafreeties that are supporting them. It is recommended that they be placed in front of normal traps so higher level monsters don't set both off, the monster being killed by the the first trap leaving the standard traps to protect the area against weaker monsters such as looters.
When used on Drull and Fomor (Level 1-2), Heavy Traps can easily kill them (as they have low health, unlike Gorgo).
Use only the Heavy Traps if a player attacks you with strong monsters that can be triggered on them.(ex. D.A.V.E.)