This is an unassuming but key event for the Sand Goblins.  You should almost always try to play both copies, especially when economy is important in a match. But there will be rare situations where it’s just better to discard.

Detonate allows you to recover all of the upgrades and the card that holds them very easily. It allows a structure that is low on life and carelessly packed with upgrades to attack, and then be detonated, to get everything back in hand and leave nothing for your opponent to kill. 

It is good to note that any rigged explosives on the card will do the damage AND return the Wrench Rat to your hand. So freely pack all explosives you can on the soon to be detonated structure. A possible tactic is to pack all such on a Bug Biter that flies to a key position, and is then detonated to get it all back.

Detonate is a key trick and economic tool that should always try to find a place when economy is important in a Sand Goblins match.