Statistics for occurrence #1 of “Bon” in chapter 2, entry boningstick of Knight's Mechanical Encyclopedia:
...stick with a head like the letter T, to indicate a level for work or construction.
A number of such sticks over a site indicate a certain level for the tops of base pieces or foundation-blocks.
Bon ing, in carpentry or masonry, is performed by placing two straight edges on an object and sighting on their upper edges to see if they range.
If they do not, the surface is said to be in wind.
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