Blast spikes could only be activated by being struck with another. To ensure their safety, users typically did this by either throwing their second blast spike or strapping it to a long pole and then ramming it into the first. Once struck by another, blast spikes would unleash a large, violent explosion.
Blast spikes were designed primarily dangerous situations in which splitting or shattering a rock was required, such as removing blockages from underground rivers or waterfalls. However, they were just as easily hammered into trees, wooden structures, and even refined stone walls.
In many deep dwarven caverns there were known to have been blast spikes placed, yet never activated, being used as a sort of climbing hold instead of an explosive. In terms of other alternative uses, some dwarves were known to utilize blast spikes as weapons.