Nail, Screw or Bolt?

“What's the difference between a nail, a screw and a bolt?” the woodwork teacher
asked Judi, the only girl in the class. Judi thought for a minute and then replied,
“Hum. I don’t know. I’ve ain't never been bolted.”
As the X-Ray technician walked down the aisle with a former patient, a co-worker Nurse
whispered to a doctor. I never could figure out what she saw in him!”
“Doctor, doctor, I keep thinking I'm a dog.”
“Well hope up on the couch and I'll examine you.”
“I’m sorry I can't Doc. I'm not allowed on the furniture.”