This is a break off thread on one on the use of an ephemeris. In it we started to talk about the different types of sundials and their usefulness. It seems best that a more in-depth analysis would fit here so I am opening one up for further discussion.
The sundial is one of our oldest and most important tools. When most people think of a sundial they think about telling the hour of the day. This was important as it told us the daylight left for activities but it was only the tip of the iceberg. A sundial can also tell us the day of the year. This is important for planning (e.g. when to hunt/fish certain areas and plant crops and for coordinating trade with other groups. The timing of most religious and civil festivals were also determined by the sundial (though some were lunar based). The sundial was also the primary tool of navigation.
Therefore it might be useful to understand the different types of sundials and their uses. Let's start with the most basic of all, the noon mark.
1. Noon MarkThe noon mark is the grand-daddy of them all. It is simply a North-South line onto which an object casts a shadow. When the shadow crosses the line, that is solar noon for that location (aka local apparent noon). For years these lines were incorporated into the architecture of buildings.
Noon mark example on a building
And it just wasn't large structures. Every pioneer home would have a noon mark. And this practice continued right into the nineteen hundreds. Even when clocks were becoming common place, the noon-mark persevered. People would paint a small circle on a south-facing window so it would cast a shadow on the floor or wall where the line was placed; sometimes drawn/painted but other times by placement of floorboards/tiles. This noon-mark was what was used to set the clocks daily!
Noon-mark dial for setting the time on watches c1760
Why was the noon mark so important? It allowed people in a given area to coordinate action. Say you had people out working in the fields. They could know when the time of the noon repast was coming and therefore when to go back to the homestead. In the same manner, those with kitchen responsibilities at the homestead knew when to have the meal ready. It also was commonly used by scouts as to know when to return to base camp. The idea being that once noon hit if you turned back you would be able to make camp while there was still light.
It also allowed people to know when events were happening in a town. An example would be to know when Sunday services were going to begin. In fact, it was standard to ring church bells three times a day, once at dawn, once at noon, and once at dusk. Many churches today continue this practice via clock time at 6 a.m., noon, and 6 p.m. It is no wonder that some of the most beautiful noon marks are within churches and other cultural institutions like museums.
The Hall of the Sundial at The National Archeological Museum in Naples was designed in the late 18th century by astronomer G.Casella and architect P.Schiantarelli 
Of course, sometimes it may have been more prudent to avoid high noon:
The noon mark is also used for celestial navigation of sea, desert, forest, and swamp. Different versions of taking a 'noon sight' have been used for hundreds of years and is still the basis for navigation today. In its current form, by knowing when local noon is, a navigator can determine his latitude and longitude from the height of the sun and the time on a chronometer. This was discussed in more detail in the ephemeris thread so we won't go into details here.
The noon mark is so ingrained in our psyche that we still break our days in half at noon. It has been proven a healthy and convenient point of reference for daily activities. For this reason the noon mark is still as relevant as ever to the homestead. And it is really easy to add one. It can be as simple as finding a tall object (e.g. flagpole, telephone pole, antenna) and placing a stone directly North of it. When the shadow from the pole crosses the stone, it is local noon. It can be as simple or elaborate as you want to make it, from just a small rock to an ornate slab.
