Q: When cutting trim, guys I work with always add a “skosh” for a tight fit at the corners. How much should I add?

A: Gary Katz, owner of Katz Road Show, editor of ThisIsCarpentry, and a presenter at JLC Live, responds: Until I saw your question, I never knew how to spell the word “skosh,” probably because I’ve only used the word on jobsites and never in an article.

Most carpenters I know also add a “hair” or a “skosh” to their measurements. I do, too, but it needs to be said that I don’t cut my material long just to make it long—if that were the case, I’d have to re-cut almost every piece. I start by measuring and cutting as precisely as possible and then add a “skosh” to those precise measurements. This is something I learned from watching a finish crew install baseboard for $.15 a foot. How big a “skosh” depends on how long the molding is. For example, if I’m installing a piece of baseboard or crown molding that’s more than 8 feet long, I add as much as ¹⁄₈ inch. I install the board by springing the middle away from the wall and letting it snap in tight against the wall, closing up the corner joinery watertight.

For boards shorter than 8 feet, I add about ¹⁄₁₆ inch. For some shorter boards, it’s just a matter of “leaving the line”—cutting to the side of the pencil mark instead of in the middle. And for really short or small pieces, like a 1-inch piece of baseboard, I subtract a “skosh,” just to be sure the piece will fit the first time. Over time, you’ll get a feel for how much to add to each board you’re installing.