Abstract: A mitre box system for cutting 90.degree. wall intersection compound angles on interior molding and similar trim without need to know the angle to be cut either before or after cutting, includes a base with upright slotted sides therealong and a rising bed pivotal upward about an end of the mitre box from a position parallel with the base to a position indicated by a linear scale on the end of the mitre box as being equal to a measured linear distance from the end of a level of length equal to the rising bed to a ceiling, one end of the level being for the measurement at the corner requiring the compound angle; each end of the mitre box has similar provisions and the base extends out at either end for clamping.