Possible Clues:

• Instrument for drawing right-angles
• Drawing board item
• Instrument used by draftsmen to draw parallel lines
• Draftsman's tool (and a hint to this puzzle's theme)
• I rule as hooker's heel stuffs fly half
• Draftsman's instrument
• Time needed with old-fashioned drawing tool
• Means of drawing a parallel
• Instrument for drawing or testing right angles
• Seen from the right angle, how odd in Ireland a backward saint would be