We keep a watch like this, that it is horizontal and the hour hand is pointing towards the sun. South is midway between the hour hand and the 12. For example, if the hour hand is at 5 minutes after 10 points to the sun, so lies south midway 10 and 12, so up 11, and an imaginary line, the one through 11 and 5 pulls, points north and south.
The Greek sage Thaies showed, that one can calculate the height of any object, by measuring its shadow and comparing it to the shadow, which a measuring stick throws.