Butterfly Back: A double looped piece resembling a butterfly that fits over a post. Variations on this design are called push back clasps. The basic post and butterfly back are usually used for stud earrings and lighter weight drop earrings.
Clip Back: A clip back is an option for those without pierced ears. There are several designs and shapes of clips, but the most common type is the paddle back. A flat piece of metal is equipped with a hinge on one end, allowing you to clip to your earlobe. Contrary to popular belief, the paddle back can be quite comfortable with the proper adjustment. If your paddle back clip earrings are too tight, insert a tweezer under the tongue (or center strip) and gently raise it very slightly. It only takes a small adjustment to make a big difference in comfort! Other options for un-pierced ears include simple clips, simple screwback clips, hinged screwback clips, mini clips, omega clips, monet clips, and even magnet backs.
Earnut: Similar to a butterfly back, an earnut has a notch in the post. Some earnuts are called "rubber earnuts" as they have a rubber circle around them to provide stabilization for a larger stud or drop earring.
Hinged Snap Back: This clasp features a hinged post that snaps into a groove on the back of the earring. It is commonly found on hoops. Sometimes the hinged post is curved to provide more room to fit around the ear, sometimes called a saddleback. Sometimes the earring itself is hinged at the bottom so that the back snaps onto the post. Some may also have a push button release.
Hook Back: This earring backing is simply a long, bent post that fits through the piercing. Hooks have several variations, from the simple earwire or threader to most notably the shepherd's hook and the French hook. While thin wire hooks reduce the weight of long earrings, making them more comfortable, they aren't as secure as other clasp styles. To make these more secure, some earrings will have a clip on the back to secure the wire. These are called wire clip earrings.
Lever Back: Made for pierced ears, a hinged lever snaps shut against the curved post to form a closed loop around the ear lobe. This clasp is very secure and good for large or medium sized styles that drop just below the ear. As early as 300 BC, the Greeks were using jewels and pearls to make earrings similar to leverbacks. They used a curved wire that attached to the earring. Leverbacks are often referred to as snap-back earrings.
Omega Back: Also called French clips, this clasp has a straight post and a looped lever. The hinged lever closes around the post and is held against the ear with pressure. The omega clasp is the most secure clasp, especially for the larger, heavier earrings.
Screw Back: This backing is a slight variation of the standard post and butterfly nut back. Instead of pushing on the back, the nut twists onto the threaded post. A screw back post design is often preferred for expensive diamond stud earrings that require increased security.