Wedging is the forcible pulling up a person's underwear (briefs) at the rear. Doing so causes the underwear to wedge between the buttocks (into the crack). Depending on the type of underwear and how the wedgie is done, it can also possibly expose the buttocks. The result is called a wedgie. Wedging can be quite painful because of the sudden pressure on the genitals.
Wedging is a common schoolyard prank in some countries, e.g. the U.S.. Usually the prank is played by a bully on another boy. Boys are more often the victims of a wedging than girls. A wedging is not only painful but also humiliating and annoying.
Wedging and spanking
Wedging can be useful in providing an effectively bare bottom spanking in situation where lowing the underwear is not desired, especially as part of a pants down or skirt up spanking. This can be less painful than the prank version, and speed is not necessarily part of it.
Lix the Babysitter, by Dave Ell (2016)