How to Set a Vertical Sundial

Place a stick upright in a level portion of ground so that it is perfectly perpendicular to the ground. Use a pebble to mark the tip of the shadow that is cast by the stick. You will use this procedure to find true North. Unfortunately, using a compass will only guide you to magnetic North, not true North, so this is a necessary procedure in accurately setting a sundial and telling the time.

Measure the length between where the stick is in the ground and the pebble representing the tip of the stick. Record this measurement with a pencil and paper.

After 15 minutes, go outside and place a new pebble on the spot where the stick's shadow has now moved to. The shadow should be slightly shorter.

Measure the length between where the stick is in the ground and the pebble representing the tip of the stick, now that the shadow has moved. Record this measurement with a pencil and paper.

Repeat Steps 3 and 4 every 15 minutes. Continue to do so until the length of the shadow is the same length as the first one you measured. At this point, the shadow will be in the opposite direction, but the length will be the same as when you started.

Draw a line between the two marks.

Draw a perpendicular line. The direction of this line represents true North.

Turn 180 degrees, so that you are facing South. Place your vertical sundial on a wall or fence that is facing in this direction. It will now accurately tell the time of day.