The dogs were the engines that pulled their sledges* (* a sledge is a special sled that hauls heavy loads instead of passengers). They are Arctic Huskies—not like dogs we know as pets—who obeyed a leader called the King dog. These fierce animals were the only way to travel in the days before snowmobiles.  Matt Henson built the sledges from a special wood called hickory. The parts were lashed together with the very strong hide from the walrus that Matt hunted with his Eskimo friends. Commander Peary was an engineer so he designed the sledges and Matt, as a carpenter, crafted them. To protect the runners from the sharp, hard ice Matt used strips of steel. But the going was so rough Matt had to repair sledges all the time.