Many modern archery pin sights come with multiple pins. The pins are adjusted to use at different distances. Use the top pin for the closest target and the bottom pin for the farthest target. You should set each pin to correspond with a particular distance that works for the types of shots you take most often.
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Start by sighting in your first pin. A typical range for a top pin is 20 yards. If you plan on taking a lot of shots at a shorter distance, you should consider sighting your first pin at a shorter distance, although the pin setting will be basically the same at 10 yards as 20 yards because most arrows shot from modern bows don't start to drop immediately.
The key is to set your top pin for the closest distance that you anticipate shooting. If you choose 20 yards for your first pin then you should hit the center of the target by sighting the first pin on target.
A modern bow sight has multiple pins because as an arrow travels it loses altitude over distance. This means you will have to aim a little higher to hit a target that is farther away. Each lower pin on your bow sight equals an increase in the upward angle of your shot in order to compensate for the increase in drop that happens as the distance between the shooter and target increases.
Typically pins are set in increments of 10 yards or so. So, you may set up your first pin to shoot at 20 yards, your next pin to shoot at 30 yards, and so on. The most important thing is that you know at what distances each of your pins are sighted. Your bottom pin will represent the pin you need to use for the farthest distance you plan to shoot.
When you are sighting in your pins you can measure the distance between you and your target for an accurate setting, but in the field it is up to you to know or estimate the distance between you and the target and then choose the corresponding pin. Consider using a range finder to take the guesswork out of pin choice or measure the distance between your stand and objects in range such as trees or rocks so that when you are hunting you can better estimate distances and decide on which pin to use.
The best way to know what pin to use is to practice, practice, practice estimating distances.
Understanding the Pin Sight in Archery
Learn about the pin sight with expert tips and advice on archery in this free video clip.