I had often desired an easy way of marking out the boundaries of a painting on a large (1.5 x 1.5m) sheet of paper - with the corners at right angles, and to be able to cut down such paintings squarely too.
I fished out my old A2 drawing board from my school days and decided the four pulley wheels on the back of the board could be used to make my own super-sized drawing board.
The prototype was a quick and dirty experiment. The walls in my studio space are brick, two are covered with white painted chipboard. On one of them I had a stretched sheet of paper ready for working on, roughly 1.5m wide, 1.0m tall. Haphazzardly at each corner I screwed the pulley wheels. A length of thin plastic coated garden wire was set around the pulleys in a horizontal figure of eight configuration. An old length of wood, the type used around door frames, was attached to the wire by staple-gunning the wire to it.
I therein discovered my first lesson: gravity! To counter this I used a pair of Mole-Grips to grip the wire by one of the top wheels to prevent the wooden ruler falling. There was no precision in this approach, but as an experiment it functioned well enough and produced parallel lines.
I proceeded by drawing horizontal lines with a pencil. Soon tiring of pencil drawn horizontal lines, I began with the paint brush, intentionally getting paint on the horizontal guide and wires.
The painting was finished in one session. Or atleast, I decided it was to be a painting made in one session, to be complete uncompleted. I liked the result. The use of horizontal and vertical lines (using a t-square), to create sections and sub-sections, injected something different into my painting and this was something I decided must be investigated further.