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 .
1 The first aircraft carriers were constructed during World War I. The first time a carrier-based airplane attacked a land target was in July of 1918 near the end of the war.  The planes used in WWI were much slower than the planes used today.