Traps in dungeon terrain can sometimes be tricky because there is usually both an undiscovered and sprung state. We envisioned a hallway that had protruding spikes on each side that could collapse together. The trigger could be anything: a pressure plate, a tripwire, a switch, and so on. We decided to use a normal wall section as the undiscovered state and special wall pieces with fixed spikes as the sprung state. See below pictures for before, during, and after triggering.
I built each spiked wall using two 1×1 floor tiles from Hirst Arts Mold #201, four 1×1/2 floor tiles from Hirst Arts Mold #201, and four of the triple-hole 1×1/2 tiles from Hirst Arts Mold #44.
Since for this build we decided to affix the walls along the center of a 1-inch tile rather than along the edge, I knew I would need the spikes to go across a half-inch expanse to reach from one wall to the other. I took bamboo skewers and cut the sharp tips down somewhat to dull them. I then inserted one into the pre-existing hole in the tile and measured the depth. I added that to one-half inch and cut six tips for each wall. After gluing the wall tiles together, I laid them down with the holes facing up so I could glue in the bamboo spikes vertically. I arranged the spikes in alternating holes so that when two walls face each other, the spikes would fit into the opposing wall’s holes. See below pictures for spike arrangement and the effect when placed together.
The end result allows any normal 2×1 section of wall to be replaced with spikes when triggered. I really like the effect in a 2×2 hallway. Since the spiked walls are 2×1, if the floor section is removed and walls pushed together, the spiked section then blocks the hallway. It is a very nice visual and presents an interesting in game obstacle.