Even in the age of the digital height gauge, a Scribing Block and Rule Holder are indispensable for marking-out. A new 6" (150mm) steel rule is accurate to ±0.004" (±0.1mm) from any graduation to its zero-end (BS 4372:1968) and typically the first 2-3 inches are graduated down to 1/64ths (0.5mm). These two items allow you to hold a rule vertically and 'click' a scriber perfectly into a graduation. Hey presto; you've marked out 27/32" without a second thought!
George Thomas' classic Scribing Block incorporates what must be the ultimate mechanism for this application; ensuring that the scriber arm can be smoothly set (from between 3/32" - 1 3/4" [2.5 - 44.5mm]) without fear of any subsequent movement.
The kit arrives with our latest drawings and build notes, together with all necessary material to produce both items and 4 spare scriber points. You'll need a tap for 5/32"x 40tpi (below) and a trusted 6" ruler.