Answer:
What kind of tree can you carry in your hand?
I help engines spin and pants stay up.
My first is a heir; My second's a snare; my whole is the offspring of fancy; which I sent out of play upon Valentine's day As a token of love to my Nancy.
I'm as simple as a circle worthless as a leader; but when I follow a group their strength increases tenfold. By myself I'm practically nothing.
I spend the day at the window, go to the table for meals, and hide at night. What am I?
No matter how little or how much you use me, you change me every month.