It's a bit expensive, but it gets the job done. The difficult part is aligning it with the ground so that the spike falls correctly. The way it works is that when power is sent to the electromagnetic valve, it pulls the spike upwards, and when the power is released, the spike simply uses gravity to fall. This model operates on 12V AC (not DC), so make sure you have the appropriate power supply. It comes with a plate with a hole for the spike. If the power goes out, you can raise the spike with the keys. It seems to be well made and looks like it will last a long time.