round trip

Margaret purchased a single round trip ticket to and from Chicago, as it was cheaper than buying two one-way tickets.

As drilling progresses, the bit gets more and more worn, till eventually it has to be replaced. In order for the bit to be replaced, the whole string has to be lugged up to the surface and taken apart section by section. Once done, the string can be put back together and the bit lowered to the well once again. This operation, called a round trip, takes most drilling crews 12 hours to complete.