Interior building materials

A method for forming an interior wall with an interior building material, the method comprising:

• bending the interior building material convexly so as to open a space capable for a blade of a cutter knife to be inserted, between a first magnetic material and a second magnetic material of a plurality of magnetic materials in the interior building material at a portion where the first magnetic material and the second magnetic material are adjacent to each other and abut each other on a base material of the interior building material;
• inserting the blade of the cutter knife into the space between the first magnetic material and the second magnetic material so as to cut the interior building material between the first magnetic material and the second magnetic material of the plurality of magnetic materials in the interior building material, along a circumference of the first magnetic material and a circumference of the second magnetic material, without cutting any of the plurality of the magnetic materials,
• wherein the cut defines a first side of a portion and a second side of the portion of the interior building material between the first magnetic material and the second magnetic material, the first side of the portion of the interior building material having the first magnetic material and the second side of the portion of the interior building material having the second magnetic material;
• and
• forming the interior wall, with at least one piece selected from the group consisting of a piece comprising the first magnetic material at the first side and a piece comprising the second magnetic material at the second side,
• wherein the interior building material comprises a base material and the plurality of magnetic materials in a sheet shape,
• the base material is in a plate shape, the base material comprises a front surface and a back surface, and a magnet is not attracted to the base material,
• among the plurality of the magnetic materials, the first magnetic material and the second magnetic material are disposed on the front surface of the base material or on the back surface thereof and are adjacent to each other so as to abut each other, and
• the base material is a gypsum board.