I think you are talking about the lower wall track. It is the curved metal part that the wall fits into.
concrete
the base is the place where the leaf joins its stem
no,cause it will break
they live underground but they are able walk around above ground.
Duck tape
You have no choice but to replace the liner
groundwater
the above portion of the earth is called the earth's crust
no
You can buy bottom rails/channels at a mobile home supply store. They are used for the skirting!
Lava
lava