Coffins and caskets are different. Coffins have 6 sides. Vampires usually sleep in coffins during the day.
Speaking of caskets. There was once this funeral and the cemetery was on top of a large hill. As the pallbearers were carrying the casket one of them tripped and the casket when streaming down the hill and rolled through downtown. As it was going through the drug store the lid popped open and the corpse said to the pharmacist, “do you have anything to stop this coffin”