A
rastrum (or
raster) is a five-pointed
writing implement used in
music manuscripts to draw parallel
staff lines when drawn horizontally across a blank piece of
sheet music. The word "raster" is derived from the Latin for "rake". Rastra were used to draw lines on
paper that had not been pre-ruled, and were widely used in Europe until printed
staff paper became cheap and common in the nineteenth century. Some rastra are able to draw more than one staff at a time.
Rastrology, the study of the use of the rastrum, is a branch of music
manuscript studies that uses information about the rastrum to help find the date and provenance of musical materials.