Answer:
A trail, a union, together tied. Come across me and you will find you cannot change the course I'm on. Without me you cannot travel on. What am I?
I have an eye, but I can't see. I usually have to work with something in my eye. What am I?
What word has kst in the middle, in the beginning, and at the end?
I am not alive but I grow I don't have lungs but I need air I don't have a mouth but water kills me. What am I?
There are four of us but it seems like everyone loves spades the most.
No matter how little or how much you use me, you change me every month.