This story was originally published on Feb. 8, 2016.

The teens who crashed while tobogganing at Canada Olympic Park in Calgary on Feb. 6, 2016, hit a chain stretched across the track that holds a movable metal barrier used to switch between luge and bobsled runs where they merge.

The crash early Saturday morning killed twin brothers Jordan and Evan Caldwell, and injured six others, some severely.

Here's how the barrier works:

There are two branches of track at the top of the hill. One branch is used for bobsled and skeleton, while luge athletes slide from separate starts on the other branch.

The two branches converge into one between Corners Five and Six and all athletes slide on the same track the rest of the way down.

The intersection is controlled by a moveable barrier made of metal and covered in hockey boards.

It's used to separate the intersection and maintain a consistent width on the track. It's secured to one wall when luge athletes are sliding and held to the other wall when the track is being used for bobsled or skeleton.

The barrier is held in place by a chain and a "come-along" winch so it does not move when hit or bumped by a sled.

The barrier is actually a safety feature for athletes — without it, they could potentially T-bone the wall on the way into Corner Six.

The barrier used to separate the bobsled and luge portions of the track at Canada Olympic Park opens to one side or the other depending on which athletes are using the track. (Erika Stark/CBC)