How does the professional term of cast iron rectangular drainage manhole covers be called

The professional term of the cast iron rectangular drainage manhole cover is called water dumplings.
The ordinary rainwater 篦: It is a steel grid.
Thisy rainwater tunnel: It is a steel grid with a steel pipe edge.
u -type rainwater tunnel: It is a steel grid with corner steel.
The anti -theft rainwater dumplings: It is to put the corner steel frame in the steel concrete, and then put the steel grid into the corner steel frame.
is generally recommended to use anti -theft rainwater dumplings.