A.Veteran carpenter Mike Shannahan of La Porte, Texas, responds: It's an excellent question. Since specifics could fill a book, I'll offer some generalities. Economics will guide most decisions. By and large, unit replacement is the less expensive course of action wherever possible. It's a straightforward job, so the labor costs are usually reasonable.

That said, rebuilding is sometimes the only option, especially when you're dealing with historic, discontinued, or custom-fabricated members. A well-equipped woodworking shop should be able to duplicate just about anything. My working philosophy is that if something can be built once, it can be built again. To avoid future rot, I mill window and door parts from well-seasoned .40 CCA-treated yellow pine. As long as it's dry, treated wood takes paint well. I leave the use of consolidants, epoxies, and fillers to others. They have their place, but my experience with them has not been overly positive.

For milling, a high-quality shaper and bench-mounted production router are musts. There are almost unlimited numbers of over-the-counter bits available, or they can be custom made by specialty tool manufacturers. I buy cutters from Southeast Tool Company in Conover, N.C. (877/465-7012, www.southeasttool.com).

Typically, I'll charge the customer for any custom tooling needed and bill on a time-and-materials basis. Since setup can be tedious, I try to mill parts for all the units at once.

Your investment in time, skill, and equipment to successfully execute this kind of work is significant, so don't be timid when billing. This is not work for the "we'll beat any price" crowd. Good luck.