What Is: License to Crenallate/Fortify

Humans have always been obsessed with showing status.  Homes, vehicles, clothing, food have all been means of displaying where one's family rested in the pecking order.  For aspiring knights and country gentry during the Medieval era, one way to prove status was the ability to crenellate or fortify ones home like the seriously wealthy and powerful barons were able to do.

Crenallations, the square-cut dips along the parapets of a castle's walls, served several purposes.  Archers could duck behind the parapet, and still have an opening to shoot down at targets below.  Embedded in the stone below the crenallated parapets were holes through which arrows, boiling water, offal or anything else could be thrown down on attackers.  However, crenellating was only a small part of any castle's overall defensive system, from the location, to the placement of the motte (tower) and bailey (walled courtyards) to thickness of walls, etc.  The ability to fortify a castle or a manor house turned into a castle depended on one's money and one's ability to obtain letters patent from either the King or certain powerful nobles, the Bishops of Durham, Earls of Chester, and Dukes of Lancaster, permitting one to add fortifications to a dwelling.  Nineteenth century historians needed a catchy name for these writs and came up with license to crenellate. 

So, we'll go with it.  Hundreds of these writs have survived in the Patent Rolls.  Most were made out to knights or men of knightly or gentry rank.  A handful were made out to women landowners.  Towns could also apply to fortify their walls.  There was a nominal fee, one mark, much cheaper than the actual building process itself.  Sources differ on why knights in particular would be so interested in applying to crenellate.  One hypothesis was that it was a status symbol.  Crenallations, whether useful or practical, definitely screamed that one lived in an honest-to-goodness castle.  One had money, and one had connections at court to obtain the appropriate letters patent.  Some landowners and towns even posted a plaque attesting to their licenses and giving the year it was granted.