The Ice Fence was a premium limited time decoration released on December 26, 2014 during the Christmas 2014 Event. It was only available until January 1, 2015.
It was released again with the Winter 2015 Event, purchasable with cash, meaning it is no longer premium.
It returned on December 5, 2017 during The Invasion Before Christmas 2017 Event as a craftable item in Jesus' Carpentry Shop. It was unlocked at level 10 and costed 40 Magical 2x4's.
It returned on December 5, 2018 during A Simpsons Christmas Special 2018 Event. 30 of them were part of the Festive Bundle and 47 of them were part of the North Pole Bundle.