solar fence post cap light  are easy to install and most are made to fit on top of a four by four inch post, which is typical for fencing or deck railings. The solar panel that is in these lights is positioned in the top of the solar post cap light so that it can absorb as much sun as possible during the course of the day. Since the panel is in the top of the light, it is not easily seen by the individuals that are around it, thus maintaining the beauty of the light while still giving great functionality.  solar post cap lights have a day/night sensor in them so that when the sun goes down, the light will automatically switch on to give light to that section of the yard. This saves on bulb life as well, since it is easy to forget that a light is still on in the morning, but the automatic sensor will turn it off and allow the recharging to begin.