Automatic Piston Lock

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Automatic Piston Lock
Temporary	no
Category	Construction Projects
Defence	15
Action points	22
Buildings required	Portal Lock
Materials required	Template:ItemIconx10, Template:ItemIcon x3, Template:ItemIconx4, Template:ItemIconx1
Unlocks	nothing
Upgradable	no

This system uses powerful motorised pistons to automatically close the gates and prevent them from opening again half an hour before the attack. Usually a waste of otherwise good nuts and bolts. Better to assign a gate keeper and a backup.