Status Updates posted by Vern Edwards
I presume that the author meant to say that the engines to be removed and rebuilt are the ones that are marked with a red tag. If so, he should have used a restrictive clause, and the sentence should have been written:
The Contractor shall remove and rebuild all engines that are marked with a red tag.
Instead, the author used a nonrestrictive clause, as follows:
"The Contractor shall remove and rebuild all engines, which are marked with a red tag."
That sentence says that all engines are marked with red tag. The clause that begins with which merely provides more information about "all engines."
The author does not understand the proper uses of that and which.