Where to put spring traps?

1.) IN BETWEEN TWO DEFENSIVE BUILDINGS say, there are 3 giants approaching your, say, canon. They will stop and attack the first cannon. After the canon is destroyed they will move to the next canon beside it. But before they move, they are grouped close next to each other (all 3 of them) so as they approach the next canon spring trap is capable of throwing the 3 of them (NOTE: a single spring trap can throw off at a of maximum 3 giants)