Corner bead is a material that is used on the corners of walls in drywall construction to make the corners crisp and professional looking. In addition to making area look neater, it also reinforces the corners, making them less prone to denting and other types of damage. Most hardware stores carry it, and there are several different styles available for people to choose from, depending on the design of the structure and one's personal preferences.
Metal and plastic are both used in the manufacture of corner bead. The advantage of metal is that it is extremely sturdy and durable, and it will last for the lifetime of the wall. The disadvantage is that metal can rust, with the rust eventually bleeding through the paint and making a rather unsightly mess. Plastic is not prone to rusting, and while it may not be as durable as traditional metal, it is easier to work with.
Classically, corner bead forms a 90-degree angle, allowing people to slip it over a drywalled corner from floor to ceiling, and then attach it once it has been perfectly aligned. It is usually only used on outside corners, with inside corners simply being taped. It is also possible to find adjustable corner bead that can be used to fit an awkward or peculiar angle, along with rounded ones known as bullnose bead that is designed to round out corners, rather than squaring them. The rounded look is favored in Southwestern-inspired design, as it evokes traditional adobe.
Once corner bead has been installed, the walls can be taped and puttied to cover nail holes, and to smooth the edges of the bead so that it blends seamlessly into the wall. Then, the drywall can be painted, with the corner bead being covered during the painting process. People may note that, over time, paint tends to chip away from corner, eventually exposing the underlying plastic or metal.
Using corner bead is not terribly challenging, but there are some important caveats to think about. When cutting it to size, people should take care to use single pieces, rather than trying to butt multiple pieces together. Butting multiple short pieces along a single corner is very challenging, and it is easy for unsightly seams to emerge, sometimes after the wall has been painted, necessitating a costly fix. Corner bead is relatively cheap, and it is perfectly acceptable to end up with some overage. It is also important to make sure that it is perfectly aligned before it is taped into place; most people like to put in a few nails to hold it to the corner, and then step back to confirm that it looks smooth and even from floor to ceiling.