Piercing taper is a special tool used for stretching body piercings. While there are several methods for stretching your piercing to a larger gauge, tapers work the best and provide the most comfort. Tapers are typically smooth pieces that have a smaller gauge on one end and then taper to the next larger gauge on the other end. There are many taper sizes, depending on the starting and ending gauge, so it is extremely important to choose the one that ends up with the gauge you want to stretch to (the one size bigger than your current gauge). Never pick tapers that are two or more sizes bigger than your current gauge, especially if you are a beginner at stretching.
Tapers are made in several common materials. There are soft ones, typically made of acrylic, and metal ones, typically made of Surgical Steel. Both are okay to use though metal ones are smoother and safer for the body. You stretch by inserting the smaller (thinner) part of the taper into your piercing and slowly moving the taper to the larger end. You may want to use a drop of emu oil to make the process smoother. Once the larger part of the taper is inside the piercing, you put the jewelry on that end (make sure to align it properly) and slowly push it inside the piercing while simultaneously pushing the taper out. Many tapers have a special flat end that makes it easy to attach jewelry to it.