Abstract: The rafter angle device includes a body in the form of a generally U-shaped plate of metal or the like having a horizontal base and spaced first and second vertical arms at opposite ends thereof. A third arm is pivotally connected to the plate at about the end of the base bearing the first arm and extends beyond the second arm. The third arm may releasably receive and is releasably securable to at least one of the first and second arms in any position between about horizontal and vertical, as by a locking nut. The first arm has a generally triangular support portion secured to the base about halfway along the length thereof and defining a spaced pair of curved slots, with angle, hip rafter valve and common jack plumb cut indicia disposed along the perimeter of the slots thereof. The support portion may also bear door sill and window sill indicia, while at least one margin of each of the three arms and base bear linear indicia in fractions of an inch.