This fits into the Medieval Cycle of Life series, after the traveling minstrel.
Today’s “Masonic Lodge” has no direct connection to the actual Freemasons of the Middle Ages, but some of the traits and tropes we associate with them, like secret handshakes and arcane knowledge only for initiates, were in fact true of the real masonry guild. Their craft was different from all others because it depended on being practiced over a large territory, and with guild members working in relative isolation. While a town guild could keep its trade secrets within a guild hall, the masons needed a way to keep secrets while traveling far and mixing with strangers.
There were three kinds of masons (though probably those three can be subdivided into many smaller parts): rough masons, freemasons, and master masons. Rough masons were stonecutters who worked in quarries, so they could be more like a normal guild whose members worked together. Rough masons could still cut stones with precision, so that ashlar blocks could be sent far away on barges and still fit together easily on site.
Freemasons could do rough-cutting, but in addition, they did decorative carving. The best freemasons are responsible for gargoyles, statues, and stone tracery that looks like granite or marble lace. Some of these went on to train as master masons, whose profession evolved into architecture.
The master mason acted as general contractor and architect. He planned a cathedral or castle, drawing plans in a special coded way that gave precise measurements for blocks that might build a corner tower with a spiral stair, ceiling arches, or buttresses. The drawings went to the quarry, where freemasons interpreted them to draw life-size models of the blocks on wide, lightly-plastered floors that acted as huge chalkboards. Carpenters cut wooden forms from these drawings, and the forms showed both types of stone-cutting masons how to proceed.
The master mason stayed on the construction site. He was responsible for choosing when tree trunks needed to be pounded into soft ground to make a better foundation. He laid out the site with pegs and strings, trying to make the corners square and oversaw digging. When the ashlar blocks began arriving, he oversaw scaffolding and foot-powered cranes. He probably did little or none of the cutting and mortaring himself, but in his training years, he had done all of these jobs.
Master masons were the most elite craftsmen of the time. In order to be well-trained, they had to work on many construction sites and in many quarries. Their art depended on exchanging information with other freemasons. A high-stakes building craft that knew only the customs of a region was limited to making the same mistakes again, so they traveled to different regions. That’s why the Freemasons Guild was dependent on secrecy and initiation. I don’t know that they literally had a secret handshake, but they had something like it, you can be sure.
Castles usually took about 5 years to build, though with money poured into the project, they could be done faster (it would mean hiring vast teams of men for every stage of the work). Some masons were hired to build a series of castles, so that most of their later career was spent in one kingdom. One famous mason, Master James, came from Savoy (foothills of Switzerland) but oversaw or otherwise contributed to many of Edward I’s castles in Wales.
The masons were specially hard-hit by the plague in 1350. Their craft never recovered; too many of the few elite masters had perished. Buildings that were completed after the plague are often notably different in their stonework of the later years.