Replacing a single brick

[autogenous]

Mick: Dunno, what's a knave?

A journeyman

The word 'journeyman' comes from the French word journée, meaning the period of one day; this refers to his right to charge a fee for each day's work. He would normally be employed by a master craftsman, but would live apart and might have a family of his own. A journeyman could not employ others. In contrast, an apprentice would be bound to a master, usually for a fixed term of seven years, and lived with the master as a member of the household.
In parts of Europe, as in later medieval Germany, spending time as a journeyman (Geselle), moving from one town to another to gain experience of different workshops, was an important part of the training of an aspirant master. In later medieval England, however, most journeymen remained as employees throughout their careers, lacking the financial resources to set up their own workshops<sup class="noprint Template-Fact">[citation needed]</sup>. In France, they were known as Compagnons.
The terms jack and knave are sometimes used as informal words for journeyman Hence 'jack of all trades, master of none' — someone who is educated in several fields of trade, but is not yet skilled enough in any to set up their own workshop as a master.

http://en.wikipedia.org/wiki/Journeyman

[autogenous]

I think German stonemasons do a 6 year University degree then travel as post graduates known as knaves to complete the degree.

[journeyman Mick]

Well, strictly speaking I'm a master but I wasn't about to use "master craftsman Mick" as my name. Besides, I like the idea of life as a journey of discovery and learning, you know "like life's a journey, man".

Mick

[autogenous]

I think Knave maybe mis-interpreted to some extent. The term Jack or Knave may have been referred to someone in Europe to be some form of Gypsy. However many trades are drilled into specialist teams in a modern world.
Many trades were previous somewhat broader in their qualification. Specialisation has allowed faster trades in certain fields.

In the field of carpentry for example specialisation has lead to:

Fixing carpenter
Staircase carpenter
Form work carpenter
Cabinet maker
Roof Carpenter
Furniture manufacturer
Wood Carver
Etc etc

A Journey man or Knave may endeavour to accomplish all these aspects. While it is possible for many carpenters to fulfill this desire carrying all the tools and "mastering" all is quite a task.
Having the capacity to carry out the tasks is one thing but the ability to make good living out of them is another.

Hence, Jack of all trades.
In medieval times a knave may have traveled the globe in search of new methods, technology and carried out a medieval equivalent post grad of his field or trade.
While trigonometry sits in common knowledge today in early times many people couldn't read or write. Trigonometry would have been cutting edge knowledge only distributed by means of Knaves etc to the world.
The Romans spoilt everything

[journeyman Mick]

Until a few years ago I was a "generalist" and took on pretty much any job that came along. I developed a pretty wide range of skills (and a huge array of tools). A few years ago, due to a variety of circumstances I started specialising in cabinets. Plain, boring, euro style boxes out of (mostly) 16mm board. Fairly uninspiring, but my customers are happy with them and, more importantly, it's an easy way to make a living with the added bonus of not too much lost time to wet weather and very little heavy lifting.

Mick