The Sheriff's Shelter is not on the original in-game map, it is more of an "Easter Egg" of sorts and is needed to complete one of the challenges for Season One - Week 3. See grid 3-AB above.
|Use the hang glider to glide through the air.
Press [F] or [Space] when you are in the air to enable the hang glider.
|Use the snowboard to move at high speed in the snow.
Press [T] to enable the snowboard.
|Use an ice axe to climb certain cliffs and use a pulley to slide up or down on the zipline.
When you are close to a climbable rock or a rope, press [F] to use.