Kiershar | Minecraft : Cheap trap with piston @kiershar | Uploaded April 2012 | Updated October 2024, 6 hours ago.
When you have some redstone and iron but no slime balls, this is the kind of trap you can do! Pretty cheap for a trap that triggers very fast. Downside is having to use gravel or sand, which looks suspicious most of times.

No redstone or iron? Make this cheaper trap :
youtube.com/watch?v=3UOIk5y6oZI