The harp is a stringed instrument that has a number of individual strings which are plucked with the fingers. Harps have strings that are tied to the frame, which is usually a triangle made of wood. Each string is tight, and the frame must be strong so that the many tight strings do not break it. The side of the triangle that leans on the player's body is called the "sound box." The top side of the triangle has a lot of pegs in it. There is one peg for each string on the harp. The top of each string is tied to one peg, and twisted around the peg. The player turns the peg to make the string more tight or less tight. This is how the player makes each string make the right note. The bottom of each string is tied to the sound box. The last side of the triangle is called the pillar. Many of the oldest harps did not have them. If the strings were too tight, they would break the harp. Adding a pillar to a harp frame makes the frame very strong, so that the strings will not break it. Christian artists often draw angels playing harps in Heaven.