On a cloudy day
The real thing: 4 m wide, 2½ m high
The sundial is on a east wall, so the gnomon only casts a shadow in the afternoon for about 3 hours until sunset. But a mirror reflects the sun in the morning for about 3 hours after sunrise. So in the middle of the day (10 or 11 o'clock until 14 or 15 o'clock) there is not much to be seen. Also high trees around the place may obsure the sun when closer to the horizon. And finally irregular plastering of the wall may introduce some slight inaccuracies from time to time.
The real thing: 4 m wide, 2½ m high
The sun reaches it rightmost position. 10:00
The sun reaches it rightmost position. 15:20
There are in fact 4 sundials in 1 drawing. Select the right lines to read the proper time. Reddish is spring (Jun—Dec), greenish is autumn (Dec—Jun). Darker colours are for the afternoon. The lighter ones for the morning, but on the real wall itself they are made lighter by being dotted.
The gnomon with the mirror.