rastrum

thumb|Single-staff rastrum 240px|thumb|right|Musical staff

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.