This article is featured in FineHomebuilding.com's Guide to Trim Carpentry.
My first construction job was as a trim carpenter's helper during school summer vacation. My boss had always worked solo, but as he got on in years (I'm older now than he was then), he wanted help moving his tools and materials. All I did that first summer was fetch and carry; I wasn't allowed to measure, cut or nail. I was told to observe. In doing so, I learned that finish carpentry is essentially a visual exercise.
Finish carpentry makes the eye work hard and skip over imperfections. At this point, the framing carpenter has made the house plumb, level and square. Or not. A good framer can ease the finish carpenter's job by providing plumb walls and plenty of blocking for nailers for attaching trim. Or not. But even if the framer couldn't read a level and and even if he added no more blocking than was absolutely necessary, the finish carpenter's job is to make the doors, windows and cabinets work, and to make the house look good.
Finish carpentry is more than interior trim. It includes siding, decking and even roofing--anything the owner will see after moving in. Rough carpenters evolve into finish carpenters by learning how to measure, mark and cut more accurately. With practice, splitting the pencil line with a sawcut and working to closer tolerances become second nature.
Perfect miters are only part of finish carpentry. Finish carpenters must develop an eye for proportion and detail. They must learn to visualize the steps that lead to the finished product. I teach these skills to novice carpenters at the Heartwood School in Massachusetts. To make learning them easier, I've organized the following ten rules of thumb.