Answer:
I come with a train and go with a train and the train doesn't need me but can't go without me.
The Titanic is still here.
I am what brings things together. Without me everything you see would be a total mass or debris everywhere. What am I?
I am an odd number. Take away one letter and I become even. What number am I?
There is one in every corner and two in every room.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.