Tools Used
- Copper Fitting: 1" for 25mm base and 1 1/2 for 40mm
- Dremel or another grinder/sharpening tool.
- Dense foam: Tall enough to cover your model
Step 1: Using a sharpening/grinding tool (Dremel) grind down the inside edge of a copper coupling. Since it is pretty soft, copper will only take a few minutes to get a good edge.

Step 2: Smooth the rough edges down.

Step 3) Pick the spot you want to puncture. Be sure to leave enough room between models and the edge of the foam.

Step 4) Gently twist and push down the coupling. You should feel it tear slowly at first then give easily to the pressure. Make sure to keep the coupling level with the foam (not angled)

Step 5) Force a dwarf to go down there!

Find anything?

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WARNING: bad pun..

Overview: I'd say it's worth trying if you have the tools lying around. There's probably other uses for this like digging tunnels in terrain or making craters.
PROS:
- Cheap and Easy (depending on if you have access to items)
- Little to no clean up
- Versatile. Allows you to place and add models as you see fit.
CONS:
- Requires a little effort at first getting the right angle on the coupling
- Some models won't fit well due to lots of out stretching limbs, parts, spikes etc.
- May cause you to make bad jokes