I have sent various emails trying to clarify actions...
The pit is 10 feet wide, 10 feet deep, 30 feet long, and has spikes all along its length. Forge is prone and stunned at the far end, just before the wall. At the far end, the spikes shot the dwarf, then more spikes filled in. The spikes before that didn't react in this manner. The dwarf has a rope tied to him.