Dear tsuwm: take a look at the description of "machicolation" in paragraph below, and see if you think it could have referred to some kind of mortar cement.

In the 13th century, defense changed from passive to active with the additions of lofty towers,
crenellations, merlons, hoardings, alures, parapets, arrow slits, and machicolations. Hoardings, also
known as bretêches, were walkways projecting out from the edge of a tower or wall with holes or
doors in the floor in order to afford the defender the opportunity to drop offensive materials (missiles,
molten lead, pitch) onto the attackers below. Machicolations (from the French machi = melted matter
+ coulis = flowing) were stone equivalents to bretêches.

http://www.manitoulin-link.com/medieval/castles.html#construction