6th Definitive Series -Text Description

What are arrow blocks?
Arrow blocks are four or more postage stamps located on the edge of a pane or sheet. The arrow resembles the letter V sideways, and sometimes serves as a registration mark for printing in two colors or more, or as a guide for guillotine or cutting operations on sheets or panes of stamps. Some arrows point to the horizontal gutter dividing a sheet or pane of stamps in half.