This commercial showed a sled being pulled by dogs across a snow bridge, which collapses in a sequential manner almost out from under them.

The snow bridge, built in miniature, was made up of "bricks" of sculpted foam. Three 10-foot long stainless steel rods held them together. With the miniature firmly locked in place, the rods were pulled out fast using a drop-weight rig. Needless to say, it was was filmed high-speed.

The top photo shows the front view and the lower photo reveals the undressed backside. We filled the big gaps with shaving cream, then dusted everything with a layer of baking soda.