Invaluable tool for determining the mesh threads per inch and also halftone counts. Place you screen on a light table and the thinly spaced lines cause a moiré pattern that point to the mesh count. Moiré will display for 300 mesh as a pattern at 150 and 100. Mesh count is probably the most often-used screen modification because it is the most predictable change to ink deposit or ink flow so this will help in the screen room or on press. Instructions included.