Answer:
I am there when you sit, but gone when you stand. What am I?
Weight in my belly, trees on my back, nails in my ribs, feet I do lack. What am I?
I have wheels and flies yet I am not an aircraft.
I look at you you look at me I raise my right you raise your left.
I have a brother. However much we run we do not reach each other.
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?