Isolator valves used to turn the water off in different situations. They can be frostproof butterfly valves/gate valves, or ball valves with different levers. In our systems, the main isolator valve installed right after the mains supply is always a frostproof valve.
Isolator valves after this first connection usually are standard ball valves or plastic cock stops.
Generally the valves can be considered open when their lever is parallel with the pipeline includes the valve. When the lever is positioned prependicular, the valve is closed. (There might be some exclusions.)
Gate valves have handwheels. When the handwheel is turned anticlockwise the valve is opening. For closing they must be turned opposite.
Brass and plastic valves/cockstops are maintenance-free, except gate valves.
Galvanised valves and gate valves are affected by corrosion, hence we advise to try to open and close them at least twice a year.