of known size, the size of objects at known distances, and even roughly compensate for both bullet drop and wind drifts at known ranges with a reticle-equipped sight. For example, with a typical Leupold brand 16 minute of angle (MOA) duplex reticle (similar to image B) on a fixed-power telescopic sight, the distance from post to post (between the heavier lines of the reticle spanning the center of the sight picture) is approximately at , or, equivalently, approximately from the center to any post at 200 yards. If a target of a known diameter of 16 inches fills just half of the total post-to-post distance (i.e. filling from sight center to post), then the distance to target is approximately . With a target of a diameter of 16 inches that fills the entire sight picture from post to post, the range is approximately 100 yards. Other ranges can be similarly estimated accurately in an analog fashion for known target sizes through proportionality calculations. Holdover, for estimating vertical point of aim offset required for bullet drop compensation on level terrain, and horizontal windage offset (for estimating side to side point of aim offsets required for wind effect corrections) can similarly be compensated for through using approximations based on the wind speed (from observing flags or other objects) by a trained user through using the reticle marks. The less-commonly used holdunder, used for shooting on sloping terrain, can even be estimated by an appropriately-skilled user with a reticle-equipped sight, once both the slope of the terrain and the slant range to target are known. There are two main types of reticle constructions: wire reticle and etched reticle. Wire reticles are the oldest type of reticles and are made out of metal wire or thread, mounted in an optically appropriate position in the telescopic sight's tube. Etched reticles are an optic element (often a glass plate) with inked patterns etched onto it, and are mounted as an integrated part of the lightpath. When backlit through the ocular, a wire reticle will reflect incoming light and cannot present a fully opaque (black) reticle with high contrast; while an etched reticle will stay fully opaque (black) if backlit. Patterns Reticle patterns can be as simple as a round dot, small cross, diamond, chevron and/or circle in the center (in some prism sights and reflex/holographic sights), or a pointed vertical bar in a "T"-like pattern (such