“So, what exactly is a plumb bob level any way?” I get asked this question most often in the gift shop where samples are on display and for sale. The masons get asked the question when they use it on the wall. Once seen in use, a guest knows what it is and how it is used. Explaining it is a little more involved. Plumb means vertical. The bob is a weight suspended on a line so it can point to the center of the earth by gravity. A level, of course, is a tool to determine if something is sitting flat or is perpendicular to gravity. If you say a stone wall is plumb, you mean vertical and if you say it is level you mean the top is horizontal.
In the Middle Ages using the plumb bob level was a well established skill. No bubble levels or lasers there! At the Ozark Medieval Fortress the plumb bob levels, as well as wooden rectangular frames for vertical plumb bobs are made in the carpenter shop. The 13-knot rope was used to lay out the triangle for the frame. The bobs are made by the blacksmith. The masons obtain the line from the rope maker. As is usual in the Middle Ages and at the Ozark Medieval Fortress it is definitely a community effort.