The practice of polling

I am interested in learning a little more about the highly dangerous practice of polling. I know that the end of the pole fits in the polling pocket on the locomotive pilot beam or rear tender beam and the other end fits on a poling pocket on a piece of rolling stock.
The practice was done to move the piece of rolling stock when it was not possible to switch to the siding or it was desirable to not have to switch to the siding.
What were the poles made out of? What was the average diameter? What was the average length?
When was the practice outlawed?
Was it fairly common or a rare occurance? I cannot imagine that crews were particularly thrilled about the practice, particularly brakemen. I would guess if the pole shifted or splintered on impact that the brakeman was either killed or maimed.
When did the practice seem to start?