Comment by rolph

Something i was told was to use the lefthand page for rough work, it [leftpage] was to be considered an appendix or attachment of sort and was not considered for scrutiny. it was highly advisable to use pencil on the left page in wet solvent conditions [water, alchohol, benzene etc.]

The right hand side of the note book was a final and standing statement of your notes and was to be indelible ink with bracket and single cross through in the case of transcription errors. the right hand page was the "final answer"