Just a word of caution: Our AutoCAD (or AutoCrap as I've heard elsewhere) dwg files reference xrefs for the titleblock, rev block, and tolerance block so that every file points to these xrefs to build the complete sheet format (SWX lingo). When these Xrefs get changed, so does every other dwg file. Originally I think our company did this to save disk space - pathetic, I know. It has the nicety in that it saves time, but we've had other issues that weren't even thought of when this method was implemented. Often times a tolerance block for a company will change as advances in machining practices and the machines themselves occur. The problem with the older drawings is that they were created with what the designer had in mind according to the tolerance block that was being used at that time. When the tolerance block change occurred, it took every drawing that was created before the new tolerance block and totally invalidated what tolerances were in mind at the time. It makes it awfully tough to look at a drawing created in 1990 and say for sure that the designer at the time was thinking of the current tolerance block - obviously he wasn't, and often it makes it hard to find out what tolerances were being used at the time - specifically for a 65 year old company. This issue comes up when a part returns from a customer in the field, and the part is inspected according to the current drawing only to find that it is out of spec. The reason it appears to be out of spec is not poor craftsmanship or that it was missed during initial inspection, but that the part was created to the original tolerance block on the drawing. At the time the part was created, it was very much in spec. In my opinion, a change to the sheet format should constitute a change to the drawing rev, so that information can be obtained later on for individuals looking at the history of the part/drawing. I hope I am making sense. Just be careful that whatever method you use - you can control the tolerances on sheet format to point to the particular ones that were used at the time. This could be accomplished by making a completely new set of sheet formats while keeping the old ones and having the old files point to the old sheet formats. That way, ant new drawings will stay current at the sheet format for the time, and the old ones will be frozen in time to what was used during its creation. If you desire to update an old drawing to a new sheet format - rev it to show what was done to the file. If you have a PDM program, it makes it really easy to look backwards in history to see the changes. Keep asking the questions Andy - this forum can be addicting to "enginerds" like myself.