Spikes can be built on the floor hotspot in an oubliette of a player-owned house. It requires 65 Construction to build. When built, the player earns 623 experience.
The owner of the house can trap players in the spikes by dropping the victim from the Throne Room above. When players are dropped, the spikes deal damage when they fall into the cage, but no more after that. This is in contrast to the tentacle pool and flame pit, which deal damage constantly to any players trapped in the cage.