ARCH MEASUREMENT INSTRUCTIONS (9-Point Method + Photo Verification)

These instructions allow any homeowner—with only a tape measure, a tight string, and optionally a laser level—to provide accurate measurements for custom arched casings.

1. Identify the Curve Endpoints (Spring Points)

1. Locate where the straight vertical jamb or opening transitions into the start of the curved arch.
2. These two points—left and right—are the spring points.
3. Mark them lightly with painter’s tape or pencil.

These two points form the base width and the starting line for all measurements.

2. Stretch a Tight String Between Spring Points

1. Drive small nails just outside the spring points, tie a piece of string so that it runs directly between the two spring points.
2. Pull the string tight so it forms a straight line between those two points.
3. This string becomes the baseline for X–Y measurements.

3. Measure the Base Width

Measure the horizontal distance between the two spring points (left to right).

Record as:
Base Width = __ inches

4. Mark & Measure Nine (9) Points on the Curve

We collect 9 coordinates (A through I) so we can accurately reconstruct the curve.

4.1 Marking the Points

1. With your tape measure along the tight string (baseline), measure and mark the string following nine evenly-spaced X-locations:

A: near the left spring point (2–3 inches in)

B: slightly farther in

C–G: spaced evenly across the span

H, I: mirroring A and B, slightly in from the right spring

The exact spacing does not need to be perfect—just roughly even.
We will calculate the exact curve from your numbers.

4.2 Taking Each Measurement

For each point A through I:

1. X-Value:
   Measure horizontally along the tight string from the left spring point to the vertical projection of your mark.

X = distance along string from left spring point.

2. Y-Value:
   At that same X location, measure from the arch curve down to the tight string using a tape or small ruler.

Y = vertical distance from the string to the curve.

Record all values using the table below:

5. Submit Photos for Verification

To ensure CNC-ready accuracy, we use your measurements to create the curve, then verify it against your photos.

Please provide:

5.1 A Straight-On Photo of the Arch

Stand centered directly in front of the arch if possible.

Hold the camera level.

Ensure both spring points and the entire curve are visible.

Include a rigid reference object at least 50″ long, such as:

• A 2×4 cut to a known length and labeled
• A strip of plywood with the length written on it
• A long level with length notated
• A door slab with dimensions notated.

Lean it flat against the wall near the arch.

If you cannot stand square to the arch:

You may not be able to shoot straight-on in tight hallways.
In that case, do one of the following:

Option A – Make a Paper Tracing

1. Tape paper (butcher paper, wrapping paper, taped printer sheets, etc.) to the wall.
2. Trace the inside of the arch carefully.
3. Fold the paper and mail it to us.

OR

Option B – Mount the tracing or template on a wall you can photograph straight-on

1. Tape your paper template to any flat open surface (garage wall, hallway end, etc.).
2. Photograph straight-on with the 50″+ reference object visible.

6. Submit Your Information

Send us:

• Base width
• All X and Y values for A–I
• Straight-on photo(s) with your reference object
• Any tracing or template if applicable

Once received, we:

1. Digitize your curve,
2. Fit a spline,
3. Confirm it matches your photos,
4. Generate CNC toolpaths for your custom casing.