There is another thing called “tracing board“. On ‘that other tracing board’ there is usually a… tracing board. That latter is the board on which the Master Mason draws his sketches and it is thus a third degree symbol. When you look at tracing boards (‘tableaus’) you will see that this ‘master’s board’ does not always have the same symbols on them. In the example above you see a plan of the temple of King Solomon and a 47th problem of Euclid. More often you will see just two symbols #X which can either be a a reference to Masonic cipher or tools to make a drawing (if you know how to use these two symbols). The most interesting examples come from Sweden:
Alright, maybe not. This is from a Norwegian tracing board.
details from tracing boards from the 18th century