Mark Mitered Stair Skirts With a Dutch Britches Jig

The Problem

A mitered skirt board — where each riser dies into the skirt with a miter instead of a butt joint — is one of the cleaner looks in stair trim, and one of the fussier layouts. Every riser's face position has to land on the skirt exactly, plumb, while the skirt itself sits at the stair angle. Measure-and-transfer invites compounding errors, and the line you need is usually on the opposite face of the board from the surface you can actually register against.

The Technique

The old-school answer is a small scrap jig — Dutch britches to some, a preacher block to others.

1. Make the jig from scrap: a flat block with a notch cut into it so it saddles the skirt board like a pair of pants — one leg riding each face, connected across the board's edge. Square edges matter; the jig's edge becomes your pencil line.
2. Set the skirt board in place on the stairs against the stringer.
3. Slide the jig along the board until its leg sits flat against a riser's face.
4. Plumb the jig with a level, then trace its edge onto the skirt board. Because the britches wrap over the board, the riser's position transfers to the face you'll cut from.
5. The same registration picks up the tread line at the bottom of each riser mark, so both cut lines for the step come off one setup.
6. Repeat at each riser, then cut your miters at the traced lines.