Serve Many But They Forget About Me
I serve many, confirmed by how healthy those I serve are. Yet after they’re successful they forget about me. It’s true, sometimes I hit them and they’re often bloody, but they don’t mind.
What am I?
A doctor (more specifically, an obstetrician) or a midwife. They deliver thousands of healthy babies but they are soon forgotten. Sometimes they smack the baby on the butt to clear the airway, and newborn babies can have blood on them from the placenta being pulled from the walls of the uterus or from an episiotomy.
The Yolk of the Egg
Which is correct to say, “The yolk of the egg are white?” or “The yolk of the egg is white?”
Neither. Yolks are yellow.
Doesn’t Fly Even With Wings
I have four wings but cannot fly,
I’ve never laughed nor will ever cry,
As much as I’d love to leave the ground,
I toil away with nary a sound.
What am I?

A windmill. The typical windmill, like the ones Don Quixote chased, have four vanes or sails. You might even say they look like wings. Windmills don’t have emotions, so they can’t laugh or cry. And since they don’t have actual wings, windmills don’t get off the ground. A well-oiled little bugger won’t make a peep.
Long or Short, Grown or Bought
I can be long or short. I can be grown or bought. I can be painted or left bare. My tip can be round or square. What am I?
Fingernails.
What Work is Never Finished?
What work can one never finish?
An autobiography. Unless you’re writing it in your death bed I suppose, but even then, how will you be able to record the time of death?