German Fuel Tank Strainer Screen (Filter) Sock, All to '74

This, filter screen, also known as a "sock" by some, is inside the fuel tank and prevents larger particles such as rust flakes from contaminating your fuel system.  It is located underneath the fitting on the bottom of the tank where the fuel outlet exits the tank.  If clogged, the fuel system can be starved for fuel.  If torn, it will allow those larger particles in where they can clog your inline filter, pump, carburetor, etc.