LATITUDE...

In the US your angle of latitude can be found Here. The angle needs converting from degrees, minutes and seconds to decimal degrees, eg 52° 30' would become 52.5
WALL ANGLE...

For a dial mounted on a south facing wall the Wall angle is 90. This is the angle the side of the gnomon makes with the wall, (line AB). The gnomon points south along line AB. So if the wall is declined 30 degrees towards the west, the wall angle on the west face of the dial is 120°, and on the east face 60°, (the two angles always add up to 180°).

Except when the angle is 90, run calculations for both wall angles. Note that when calculating for shadow angles with the dial west face, the resultant marking out of the west face will be for the morning sun as it comes up from the east.

LENGTH BC...

This is the vertical length of the gnomon where it joins the wall.

DECLINATION...

The range is 23.44 for the sun's highest point in the summer, to -23.44 for the mid winter sun. The equinoxes have a declination of 0. On the dial, the lines of declination across the dial face are tracked by the shadow from the end of the gnomon, point `A', this shows as the tip of the shadow at point `F'.

HOUR ANGLE...

One hour is represented by 15 degrees, (360/24). Multiples of 15 up to 90 represent the range of hours on one side of the the dial. West face and east face being calculated separately except when the wall angle is 90. Any fractions of angles can be calculated.

GNOMON...

The geometery of the gnomon is shown as lengths 'AB' 'AD' 'BD' and 'CD'. And angles 'ACD ' and 'BCD'.

Length 'AC' represents the shadow casting style of the gnomon. Length 'AB' projects from the dial pointing south. A gnomon can be made as triangle 'BAC' or 'DAC'.

SHADOW...

The shadow angle, is measured from vertical line 'CG' and radiates from point 'C'

The length of the shadow, as measured from point 'C' to point 'F' (shadow length CF) is affected by the declination for a given wall and hour angle. Distance 'FG' and 'CG' can be used as an alternative way of finding point 'F'.