Each of us more than once or twice noticed and walked on the streets of the open entrances to the city’s underground utilities, sewer and other wells. And…
City underground communications, dangers and safety prevention.
breakthrough
Breakthrough, die and mallets, opaque portable airplanes for ermine, squirrel and mole, device, principle of operation, dimensions and manufacture.
To portable opadnyh airplanes is a slip made of two boards (scheme a). At one end, they are connected by ribs with a rope loop, and at the…