KhannaOffice publishes unigrid.app.

unigrid.app generates the Unigrid B6 sheet and lets you compose on it: a trim of 420 by 594 mm, modules of 84 by 80 points on intervals of 12 by 10 points, twelve columns and seventeen exposed rows, the 100 point title region at the head and the 25 point bar at the foot, every number of it resolved from the 1985 specification. This first version composes both sides of the sheet, sets the title band on either or both of them, places photographs, words, colour and divisional bars in whole modules or half modules, and runs a photograph or a colour past the margin to the trim when you pull it there. It exports the pair as a PDF at the trim size, and each side on its own as a 300 dpi PNG or as an SVG. It is built on @khannaoffice/unigrid 1.0.0, it is free to use, and it keeps your work on your own device.