You probably won't need a corner ladder very often while painting a house, but if the circumstances arise that you need to set a ladder directly against the vertex of a corner of a building, an ordinary ladder just isn't really the proper tool for the job. In a case like this you need a corner ladder
A corner ladder is a ladder with extension arms at the top of the ladder that extended outward and forward so that the end caps of the two arms rest against the two sides of the building that form the corner.
Corner ladders may be designed and sold as corner ladders,
however most corner ladders are actually standard ladders with a device
called a corner stabilizer installed on to them.
Corner Stabilizers are usually made of aluminum with rubber or plastic end caps. They are generally inexpensive easy to install and remove, and often no tools are required to use them.
Corner Stabilizers are sold separately and can be mounted to most extension or single section ladders. However some specialty ladders and step ladders may not be suitable.
These corner stabilizers may be available at some hardware and paint stores, but where there is not all that much call for these things they are usually harder to find than most climbing equipment. If you need a corner stabilizer and can not seem to locate one try a store that specializes in ladder and staging equipment... or you can order one from an internet store.