How to Scribe Arches

Setup

• 1

  Mark the first end of your arch by driving in a 2-inch finish nail at the point you want your arch to begin. Drive the nail in far enough to stand firmly erect with a string tied to it and stretched to another nail.

• 2

  Measure from the first nail using a tape measure to the point that you want your arch to end. Use a straight edge to ensure the end point is directly across from the first point. Drive a second nail in at the point determined for the end of your arch.

• 3

  Measure between the two nails and mark the point directly in the center between them. Use a square to measure up from that point to the height you determined for the arch. Mark a point at the top measurement of the arch. Drive in a third nail at this point.

• 4

  Tie mason's twine to the first nail snugly. Stretch the mason's twine up around the third nail that you positioned at the top center of the arch and back down to the second nail you positioned at the end of the arch. Tie the mason's twine to the nail at the end of the arch to create a "tent" form between the three points.

Scribing

• 5

  Stand your scribe tool up vertically against the first nail so that it rests against the string. Draw the scribe along the string, pressing out slightly, creating a curve up to the center point of the arch.

• 6

  Continue drawing the scribe along the string, pressing out on it evenly. Press firmly on the scribe tool, creating a depression along the curve of the string. Draw the scribe up to the center point and start again, scribing a second arc down to the third point to complete the arch.

• 7

  Untie the string and use locking pliers to pull the three nails from the surface.