How many types of gate valves are classified according to their structural forms?

Gate valve--rising stem gate valve and non rising stem gate valve

Rising stem gate valve--wedge type and parallel type
Wedge type - resilient gate valve and rigid gate valve
Rigid gate valve - single gate valve and double gate valve
Parallel type--rigid gate valve
Rigid gate valve - single gate valve and double gate valve

Non rising stem gate valve--wedge gate valve--rigid gate valve
Rigid gate valve - single gate valve and double gate valve