Koshitazu (small sketch) refers to the many small sketches that are drawn to plan out the image and direction of a painting before starting on the actual piece. It is also called kojitae or esquisse.

Koshitazu is prepared to determine the composition of the work from sketches and to examine ideas and images in the artist’s mind. New sketches may be prepared based on this examination.
Keeping the sketches relatively small makes it easier for the artist to grasp and cogitate on the overall picture, and helps in the process of building up a clear image of the work. As the sketches are small, they are also easier to work with.

For example, a rectangular frame can be drawn on a sheet of paper in a Croquis book and sketches drawn inside. The artist can use the entire sheet or prepare several small frames on the same page to make comparisons. Another way would be to do the sketch first and add the frame later.

Pencils and Conte crayons are used for this but the sketches can be colored using colored pencils, watercolors and pastels if the main focus is to check the correlation of the colors.