A 45 is a song any song which does not mention the sound name as opposed to a dub plate which has to mention the sound name. In a 45 shootout, sounds clash by selecting and juggling their best choice of songs backed by a good MC (for this clash it is anything goes but the sounds have to read the crowd in their selection). The sound that gets the biggest forward from the crowd takes the day.
The secret to a 45 shootout is reading the crowd and knowing what they prefer. Having a good MC to present the song as the selector plays is a plus. It helps horn the selector by making him dig dip into his tune library looking for rare hits than can move the crowd.
One of the major rules of a clash is “no playback” simply meaning that a sound cannot play a song that has already been played by the competitor. This in itself means that the selector has to do a lot of research and go dip into his song library.