A spyglass is a handheld telescope used by sailors in navigation, as they made it easier to see outward, identifying other ships and spotting land. They were designed with a wooden or metal case, which contained lenses that would magnify the image of the distance. They were constructed with collapsible components, and varied in size. Brass is a popular material in their construction, as well as that of other navigational tools, due to its corrosive- resistant nature.
On both land and ships, lookouts are typically stationed in high places such as hills or in the rigging and given a spyglass in order to properly survey the surroundings.