easy
All day long it's in and out. I discharge loads from my shaft. Both men and women go down on me. What am I?
Common Wrong Answers
“A bus”
While a bus carries passengers in and out, it doesn't have a 'shaft' and the phrasing of 'discharge loads from my shaft' does not apply.
“A train”
A train does transport people in and out, but it typically runs on tracks rather than having a shaft, and the phrasing about discharging loads is not relevant to trains.
“A well”
A well does involve the concept of going down and bringing things up, but it does not have a mechanism for discharging loads in the way described in the riddle.