Answer:
cats and deflation tires make this noise.
I am constantly overlooked by everyone but everyone has me.
What has feet and legs, and nothing else?
I help engines spin and pants stay up
I come in different colors and shapes. Some parts of me are curvy some are straight. You can put me anywhere you like but there is only one right place for me.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.