What type of manhole cover is provided in the water tank in your house,a cement slab or an iron cover?

Most of us are ignorant of some details about our own house.
Fresh water and sewage systems are among them.
In the tank top if a cement slab or iron cover is not secured with a hinge or some locking arrangement,
It is very dangerous.A heavy wind will drop it on someone’s head.The safety on this is generally ignored by builder and Government.

Any breach of safety you have noticed in your house or other buildings?