To build a igloo all you need is some hard dry snow and a large knife or snow saw. Cut numerous blocks approximately 3 feet long, 8 inches deep and 15 inches high. Begin to stack the blocks around the hole created from the area where you cut out the blocks of ice. Stack the blocks in a circular fashion, shaping them inwards and creating a dome shape. When the dome is created the final top block should be larger than the hole, cut and shape the final block to fit the hole. Dig a hole under the wall that comes out on the outside of the igloo, this hole is called a cold sink. Be sure and make some ventilation holes inside the upper walls of the igloo. Body heat and heat from a fire will cause the snow on the outside and inside walls to melt and refreeze causing the wall to solidify. You may want to build a small roof over the outside opening to keep snow from getting inside. Enjoy your igloo!