Felting needles are small, barbed needles used in felting wool. By poking the felting needles repeatedly into loose wool, the wool becomes compact and can be shaped. This technique is called "dry felting."
Most wool is wet felted—that is, strands of wool are knitted or woven together, and then the fabric is soaked in water. The fabric is then pounded until the wool fibers entangle into one sheet of wool. The felt will shrink as it dries, further binding the fabric together. Felting needles also take advantage of wool's predisposition to entangle itself, but the technique uses pressure instead of water.
Felting needles, like sewing needles, come in a range of sizes, though all have barbed tips which help to tangle and compress wool fibers. The different sizes allow for various amounts of control when sculpting. Felting needles can also be mounted in a circle on the underside of a wooden handle so four or five of them can be used at once. This helps to sculpt large, three-dimensional figures out of wool.
The use of felting needles has been called both a very easy and a very hard technique to learn. It's simpler than many projects in that dry felting really only requires the needles, a foam board, and some wool. Stabbing wool with a needle over and over is not a technique that requires a great deal of skill, but making even a simple shape requires thousands and thousands of jabs in order to get the wool fibers to knit together. Each jab should only go down about a fourth of the depth of the yarn, not punch through it.
Possibly the greatest asset needed to learn the proper use of felting needles is patience. Once these skills are learned, mastery of the needles allows the crafter to make everything from flowers to sculpture. The needles can meld two different colors of wool together or attach small pieces of floss or cloth to the finished piece without using glue.
Since felting needles are sharp, unskilled crafters need to be careful not to injure themselves when using them. Sometimes felting guides recommend that the user get a tetanus shot before using these needles. It may also help to invest in a foam pad to set the wool on while shaping it. This will prevent the needles from breaking on a hard tabletop or from slipping and stabbing the user.