1 Discard any hammer with mushroomed or chipped face or with cracks in the claw or eye sections. 2  Wear safety glasses or goggles, or a face shield (with safety glasses or goggles).  Strike a hammer blow squarely with the striking face parallel to the surface being struck.
The first jet airplane was the Heinkel He 178 made in Germany in 1939, right before the outbreak of World War II .
A+E Networks. On this day in 1949, the worldâs first jet-propelled airliner, the British De Havilland Comet, makes its maiden test-flight in England. The jet engine would ultimately revolutionize the airline industry, shrinking air travel time in half by enabling planes to climb faster and fly higher.